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Luffy's two dominant traits are his apparent lack of intelligence and his utter fearlessness. Luffy can easily be amazed by the simplest things, such as hermit crabs, and can be confused by concepts such as that by digging a hole right next to another he may be unintentionally filling the other hole. He likes monsters and will ask weird creatures to join his crew (as seen in the Thriller Bark Arc, asking a talking tree to join his crew). He also has no knowledge of medicine, when Nami had a high fever he told her to eat cold food and later tried to make Roronoa Zoro better (after battling Bartholomew Kuma) by pouring sake onto him because Zoro likes sake. When attempting to think up a plan to get off of Amazon Lily, while he managed to make some logical sense of where to look, he is seen to strain himself and notes that he is going to feel sick from too much thinking.
His simple mind actually saved him against Hancock's powers because he mistook it for a "Noro Noro Beam", which was used by Foxy, which brought out a fear of being slowed down (though it is shown later he is simply immune to her powers, because of his pure heart). If Luffy finds something he does not understand, even if someone explains in detail, he calls it a "mystery thing"; like calling Dance Powder a "mystery powder". One of Luffy's running gags is asking "non-humans" such as Keimi and Brook if they can poop, in which case the answer is usually a yes. Another running gag is Luffy's slow reaction time, especially to freezing temperatures.
The same cannot be said when he is on the field of battle, though; he has been known to dodge bullets with ease. It has been stated more than once that Luffy's instinct and behavior is similar to that of a wild animal's, like when he knows who he has to fight before he even gets to the battle. Even his fights show this as he relies on his instincts and counter attacks. This compliments the way he views the world. He is most often seen smiling, except in a fight where he is forced to use all his power (and sometimes even then). Luffy also seems to rarely change personality wise. Because he views the world in a straightforward and simple manner, he is occasionally the only person who can see past events that have taken place and realize the true goal, yet at other times he can fall into the simplest of traps.
He is, however, a genius when it comes to fighting, such as when he figured out how to defeat Crocodile's Devil Fruit power on the verge of death, how to use Soru from sight, developed a number of effective counters to Enel's "Mantra" ability and, most recently, learning everything Silvers Rayleigh had to teach him about Haki in a year and a half (even though Rayleigh mentioned that two years were too short a time to learn about Haki). He does have a habit of holding a grudge even in dire situations, such as calling Franky a "bastard" in the middle of his fight with Rob Lucci causing Franky to retort "Now's not the time to be mad at me" and refusing to let Crocodile help him escape Impel Down (even when there was no alternative). However he tries not to hurt civilians and people he likes, even if they intend to do harm to him, preferring to run from them than fight.
When drawing him, Oda has said he tries to make Luffy very straightforward about what he wants to be and how he feels, which is why out of all the main characters, he has the least number of thought bubbles, since he acts and says what he wants to do rather than think it. To compliment Luffy's naïveté and straightforward attitude, there is a running gag through the series where Luffy can identify similarities on things that have little resemblance (like being able to see the resemblance between Sanji and his Wanted Poster, or being able to see Spoil as an old man with major wounds rather than a zombie), but is unable to see similarities with things with obvious connections (like being unable to tell that Sogeking is Usopp or not seeing through Foxy's pathetic disguises).
Luffy's simple attitude and naïve comments during fights are often mistaken by his opponents as poking fun at them. Due to this, many of his opponents lose their cool and charge at him in anger. While he is goofy and reckless, he gets quite serious when anyone is in serious danger, notably his crew, whom he considers his family. Luffy also has the tendency to unwittingly poke fun at an opponent's most sensitive trait, like calling Buggy "big nose", Alvida "the fat lady", and Kureha "old hag". In many cases, the opponents fail to understand whether Luffy is serious or just playing during fights due to his bizarre actions like drinking too much water in his fight with Crocodile or punching out Arlong's teeth and using it as a weapon to bite him. Luffy, however, has maintained that he is always serious during fights. In most cases, once he starts to fight he maintains a serious attitude and is only seen laughing once he defeats the enemy or is certain the enemy will be defeated, like in Buggy's case when he laughed before sending Buggy flying in the air.
Every time Luffy defeats an antagonist or an enemy, within one or two chapters, whether it is because something entertaining or comical happened, Luffy smiles. There has been only one exception: after his fight with Usopp in Water 7, Luffy did not smile for the longest time in the entire series while non-combative; in the storyline, he did not smile for a whole day, but in terms of chapters, he did not smile for fifteen chapters.
In battle, Luffy has shown signs of intelligence, high tactical and innovative skills. He can easily adapt to hindering situations such as Mr. 3's Candle Lock or Enel's Gloam Paddling into an attack. He also used a mirror to reflect Foxy's Noro Noro Beam attack. During the Marineford Arc, Dracule Mihawk mentions that Luffy seems unusually clear-headed by avoiding Mihawk's attacks. Additionally, during his battle against Mihawk, he uses Buggy as a scapegoat shield to help protect him and move forward towards Ace. Luffy also has a habit of saying things with a lot more weight and (occasionally) wisdom than he realizes without even thinking or meaning to.
Luffy also shows significant leadership skills, which at other times he usually lacks and therefore has his captain duties done by another crew member. An example of his leadership is usually present at the most dire and serious times. Such as in the Water 7 Arc in which a portion of the Straw Hats, some Galley-La foremen, and the Franky Family are present. Luffy brings the three together by pointing out that they now have a common enemy and should form an alliance to take back what the enemy has taken. Another time could be when he takes on the burden of being a Captain and does not hold back when dueling Usopp, and restrains himself from calling Usopp back afterwards. Crew members also listen to his orders without question when he is serious, all respecting his position. In the Sabaody Archipelago Arc, Jewelry Bonney comments on how not just anyone could order Zoro around, since Zoro seemed to be so independent and ruthless. Yet he respects Luffy's commands when the time calls for it.
The one thing that Luffy does not allow is someone or something getting involved in another person's fight. At these times Luffy shows both remarkable restraint during the battles, and rage when something or someone outside the battle is involved, especially if it is a person he considers a friend. Luffy showed this early in the series when Zoro fought Mihawk, and managed to hold himself (and Johnny and Yosaku) back until Zoro was defeated. Since then he has shown it several times, like when Baroque Works sabotaged the giants' duel on Little Garden; when Crocodile attacked Yuba with a sandstorm in the middle of their fight; when he challenged Aokiji to a 1-on-1 fight; when he fought Lucci and insisted that Franky does not get involved in their battle; when the Boa sisters threatened to break the petrified form of his saviors; and when he was visibly enraged with Hody Jones who attacked some civilians who tried to halt Noah. He even went so far as to cover Sandersonia's back from the citizens of Kuja while it was still burning, even though they were trying to kill him, claiming it has nothing to do with their fight.
A bit of a running gag is that during battles, Luffy is almost always thrown into situations, by accident or on purpose, where he cannot fight. When he is in a situation like this, his crew members usually fight the other, weaker people associated with the main antagonist, and defeating them, so that there is no one to interrupt in Luffy's fight. Then, when all the other enemies are defeated, Luffy fights the strongest, i.e. the one that only Luffy can defeat. This happens frequently, such as him being stuck in a cage in the Orange Town Arc, being put to sleep in the Syrup Village Arc, getting stuck in a rock and being thrown underwater in the Arlong Park Arc, getting lost, getting seriously injured and resting, or getting stuck in a snake's stomach in the Skypiea Arc.
Luffy's personality is like that of a child's, in the sense that he tends to go to the extremes. He can either be extremely greedy, especially in cases of food, who his crew is, and adventure; or extraordinarily selfless, going so far as to virtually sacrifice himself to avenge or protect his friends, crew, and family. This childish mentality of his allows him to get to the root of the problem, and allows him to figure out the most simple way of solving it.
Luffy also has an extreme thirst for adventure, which he has stated is the main reason he wants to become the Pirate King, having the belief that the Pirate King would be the one on the entire ocean with the most freedom for adventuring. Because of this adventurous nature, he tends to avoid taking 'the easy way out' at times, such as when he destroyed the Eternal Pose to Nanimonai Island given to him by Robin (Miss All-Sunday at the time), stating that he did not want an enemy to decide his destination. He also has no intention of trying to learn what or where One Piece actually is until he finds it himself, and once stated he would quit being a pirate if his crew tried to find out, not wanting to 'go on a boring adventure'. Luffy has no actual sense of caution and in fact, has been known to literally laugh in the face of danger and walk into potentially harmful situations with a massive grin. For example, when the Straw Hats approached the Knock-Up Stream and when they decided to board the Rumbar Pirates ghost ship. Also when entering Thriller Bark and while descending to Fishman Island, Luffy never says goodbye to those he considers friends, in hopes of seeing them again.
As a person with the middle initial D., Luffy shares the common trait of not fearing death. He will often state that if he reaches his goal, that's fine, but if he dies on the way, that's fine too. He even smiled when he was nearly executed by Buggy in Loguetown, although he did have a look of shock and surprise in his eyes before this happened when Sanji and Zoro tried to rescue him. Throughout the series, several characters have stated similarities between Luffy and other D. carriers, whether in personality, words, actions or presence. So far he is thought to be similar to Jaguar D. Saul by Nico Robin; to Monkey D. Garp by Aokiji, by at least one of the Gorosei, and by his own crew; to Monkey D. Dragon by Emporio Ivankov; and to Gol D. Roger himself by Smoker, Crocus, Kureha, Gan Fall, Shanks, Rayleigh, Kokoro and the non-canonical Raoul.
Like other D's so far, he is also quite a glutton despite his skinny appearance: he especially loves meat and can eat a fish whole - bones included - and because of this, a running gag of Luffy's is him constantly stealing other peoples' food with his rubber powers, causing them to yell at him and sometimes hit him. It should also be noted that he becomes more gluttonous over the series as there are moments he becomes morbidly obese, though he loses the weight in some way, usually exercise. Also, after the events of Enies Lobby, Luffy seems to have developed narcolepsy, much like his brother Ace, though for only a short time.
Another running gag is his habit of being amazed at various abilities of villains, often yelling out "amazing" with stars in his eyes and around his head. Luffy believes that he is at his "coolest" when he is wearing armor. Luffy also seems to have a slight obsession when it comes to outfitting himself with full-body armors, and has a habit of wearing one whenever he gets the chance. But every armor that he manages to find and outfit himself with usually ends up destroyed either in a battle or by some other comedic scenario. He also constantly insults his opponents by giving them degrading nicknames (such as calling Gekko Moriah a "leek" or Enel "earlobes"). Luffy apparently has no skill with insulting people, usually taking either a physical aspect or unique ability and trying to make it degrading (like calling Zoro "three-swords style" when everyone was lamenting Vivi's absence, only to be corrected by Usopp).
Luffy also has absolutely no talent for lying whatsoever. In fact, more often than not, Luffy would blurt out, without thinking, what he knows regarding a certain event whenever someone asks something concerning the events that transpired. In contrast, Luffy has a tendency to suck his lips in and turn his head to the side when an attack or technique fails to affect him, such as Enel's various electrical attacks or Boa Hancock's Mero Mero no Mi.
Luffy never kills any of the villains (no matter how cold-hearted they are); instead, he frequently sends the villain flying, knocking them out or beating them until the point that they are almost near death. Oda explains that it is not a question of morality so much as a matter of punishing the villains for their crimes - he feels that killing the villains lets them off too easily, whereas he considers letting them live to see their dreams ruined a far more fitting punishment; however, it is evidently clear that Luffy is not against others completing the final act themselves, as seen when Luffy allowed Law to make his attempt to kill Doflamingo, while making sure Trebol does not interfere. Ironically though, some of the people he has defeated have become good after their defeat, most noticeably Wapol becoming a rich CEO of a toy factory, though he possibly became evil once again after he created his new kingdom.
Another dominant trait of Luffy is his humble nature: he does not brag about the powerful foes he's defeated in the past, though he's not above about claiming that no one has ever beaten him in the past (which is not true, having been defeated many times by Ace and Sabo as a child, twice by Smoker (though non-fatal), twice by Crocodile before defeating him, once by Aokiji, once by Rob Lucci before defeating him, once by Gekko Moriah before defeating him, once by Bartholomew Kuma, once by Magellan and once by Kizaru, all in the past). He remains humble despite having done outrageous acts like defeating Shichibukai-level pirates and issuing the order to burn down the World Government Flag back at Enies Lobby. When Franky pointed out the latter, Luffy only replied that it was nothing to get worked up over (hinting that he only gave the order on a mere whim), for he and his crew were only there to take back a crew member that was taken from them. When Sengoku tried to cover up Gekko Moriah's defeat by ordering Bartholomew Kuma to kill the Straw Hat Crew, Vice Admiral Garp told him, "Ah, do not worry yourself Sengoku! Luffy is not the sort of guy who'd go around boasting about taking out Moriah anyway!".
Despite his passion for fighting, Luffy also generally refuses to fight someone that he does not personally consider an enemy, preferring to either talk it over or run away from the confrontation. Over the series Luffy has become more mature and levelheaded, though he only shows this part of his personality when he and his friends are in dire situations or someone insults him, calling people like him and their beliefs foolish; other than that he still acts the same as he was at the start of the series.
He almost never gets irritated with normal people, though there are a few exceptions, like when they seem to have an opposite taste in food as he, or when they ask if they can take a look at his "privates". Luffy also has no problem with other people stretching and playing with his rubber body, however, he does get a little irritated if they are doing so while he's in the middle of eating. Luffy calls every mixed-appearance creature he finds by whichever creature is its secondary (non-dominant) part. On Gaimon's island, the dog/chicken was referred to as a chicken when it was mostly a dog, the snake/rabbit a rabbit even though it was mostly snake, and the pig/lion a lion even though it was mostly pig. This becomes a running gag: later when he meets Bananawani, he calls them bananas with crocodiles attached to them. Also, after seeing Pierre transform, he continued to refer to him as a "horse" instead of a bird. And related to this running gag, when on Long Ring Long Land island, he called every animal by what he thought they resembled rather than the actual species they were.
Luffy's interest in women is a complex matter: in an SBS, Oda stated that the reason Luffy acted in an aroused manner when Nami stripped, yet remained neutral when Hancock did so, was that he was with Usopp at the time Nami did so, as Usopp is his age and a bad influence on his behavior. He also appears to have little or no romantic interests, having nonchalantly refused the proposals made to him by Lola and Hancock without a second thought. Ironically, despite his lack of interest in women he has attracted several along with his travel such as Alvida admiration, the love by Boa Hancock, and the affections by the women of Amazon Lily.
Luffy is very loyal to his crew-mates and other friends, and can lose his temper quickly if they are harmed in any way (a trait that he apparently shares with the late Pirate King). Luffy is willing to do drastic things to avenge and defend those dear to him, even if it means breaking a promise to his friends, such as striking Bellamy down for attacking Montblanc Cricket's crew, and punching World Noble Saint Charloss in the face for shooting Hatchan, despite promising not to defy the World Nobles. Additionally, Luffy believes that all people should be loyal to their friends, and if Luffy sees anyone betraying their own comrades, he would stand up for the victims (even if they are enemies). Notable examples of this are Captain Kuro killing his own crew, Don Krieg attacking Gin, Boa Hancock petrifying her fellow Kuja tribe members, and Caesar Clown using his subordinates as mere guinea pigs.
Luffy has gained a reputation for being extremely reckless, and in some cases, insane. However unlike other pirates who gained a reputation for being psychotic (like the Marine-killer Caribou, or Bellamy) through needless and random acts of violence against civilians or the authorities, Luffy's reputation comes from him trying to help or save others, especially in the face of authority (though he does tend to go overboard).
Luffy has shown to admire heroes, though has stated vehemently that he really does not want to be one, his reasoning more-or-less translating that the definition of a good hero is to be entirely selfless. Ironically, many of Luffy's actions are mostly selfless, with his selfishness mainly revolving around his gluttony and his thirst for adventure. This trait leaves everyone he meets with to think he is some kind of hero, but not by his own design. However, he is easily convinced by Jinbe for his plan of becoming a hero of the Fishman Island with an agreement of meat.
Luffy's apparent selflessness often inspires others to side with him as a result. Notable among these people are Boa Hancock, Jinbe, and Emporio Ivankov, who would not have helped him out otherwise, given their individual beliefs. He also shows respect for things that a person is willing to die for, be it a treasure or a secret, to the point of even fighting to protect that which the person would throw their lives away over. The most noticeable action of this would be when he protected the Gorgon Sisters' secret by using his own body to cover the mark on Boa Sandersonia's back, even though they were trying to kill him.
However, despite all his peculiar traits and habits (with his trademark dimwitted behavior), Luffy's most defining part of his personality is the ability to make allies out of absolutely anyone (including former enemies, villains and even Whitebeard himself), which is said by Mihawk to be the most dangerous ability in the world.
When other individuals heard Luffy mention that he, his crew, and the people they meet are friends or comrades, it touched the hearts of others who were later grateful to Luffy and his crew and support them, like Carue, Vivi, Nefertari Cobra, and Fukaboshi. That also applies to Nami and Chopper who later joined the Straw Hat Pirates.
Also, as a bit of a running gag, Luffy, when talking about money, tells his crew-mates to budget their money, only for them to react in return that it all goes towards feeding him. Another running gag involves Luffy randomly telling someone a secret, such as the identity of his and Ace's fathers, only to casually ask them to keep it a secret afterwards. He shares this trait with his grandfather.
When his adoptive brother Ace was killed at Marineford, the mental strain of watching Ace die in his arms caused him to fall into a catatonic state. After waking from this state, Luffy flew into a rage and went on a destructive rampage to vent his grief and anger.
Afterwards, Luffy re-evaluated himself and came to the conclusion that he had been too naïve, and was weak and unworthy of becoming Pirate King, falling into a state of depression and self-pity. Some encouragement from Jinbe and Rayleigh gave Luffy some renewed courage to continue pursuing his dream. After the timeskip, he tells Rayleigh that he will be Pirate King, having regained his confidence to fight for his dream.
Prior to the timeskip, Luffy had displayed a side to himself where he occasionally gets into fights with others over needless issues (i.e. he nearly got into one with Blackbeard in Mock Town over a matter of quality of the pies that the tavern served to their patrons). He still has this trait after the timeskip when he is shown to fight with Momonosuke when he arrives on Dressrosa. However when Luffy is told to keep a low profile or to restrain himself he will resist his urges to pick fights over small matters.
Because he is the Captain and recruited all the crew mates personally, Luffy cares tremendously for his crew. As far as captaincy is concerned, Luffy sees his other crew mates as equals in contrast to other pirate captains, who mostly sees theirs as subordinate underlings (his crew mostly calls him by name, rather than with an honorific or "Captain"). In fact, it could be argued that he is the only one that is generally beaten up and ordered around on the ship as several members of the crew have shown, especially Nami who never hesitates to give Luffy a beating for his idiocy (albeit, in comedic fashion). Luffy only pulls rank when he wants to go "adventuring", despite what his crew thinks, examples being when wanting to go to Skypiea and following the swaying needle to the New World.
Much like his idol, Shanks, Luffy is the kind of benevolent pirate captain who does not seek to actively harm others unless they give him and his crew (or anyone he cares about) a very good reason to. However, during the Jaya arc he was willing to start a fight with Blackbeard over a difference in opinion on pie. As the Straw Hat Captain, Luffy has utmost faith in his crew. In fact, after the timeskip, Luffy's trust grew even more as shown when he overheard that his crew were being apprehended by the Ryugu Kingdom's guards, he did not seem perturbed at all, and was confident that his friends could take care of themselves. This is seen once more when he accepts Law's proposal for an alliance. When his crew confronts him about it, he claims that even if Law is untrustworthy, he is not worried because of the faith he has in his crew and the training they put in during the time-skip, eliciting a shock from them before reacting positively to his praise. Luffy also has the rare ability to cheer up just about anyone with his idiotic antics, even pulling a smile every now and then from the serious Zoro and Robin.
In turn, his crew, while often frustrated at his immature and impulsive nature, trust him unconditionally. They also show great concern for him when he is put in life-threatening situations. It can be said that Luffy has both greatly impacted and changed the lives of each of his crew members and is typically the one cited as having revived each of their dreams.
During his battle with Lucci, even though Luffy knew his crew were in danger (courtesy of Lucci flooding the tunnel) he kept fighting Lucci because they would manage and because Luffy knew that if he let Lucci get away, he would definitely kill all of his crew. This focus caused Lucci to compliment him on his leadership skills.
Though all of Luffy's crew tries to look out for him, due to Luffy's reckless and carefree attitude, on numerous occasions a crew member might wonder why they followed such a crazy captain. However, by the end of the day (or adventure), none of them truly regret following him and generally enjoy being in the crew. He likes to make fun of others' imperfections and character traits, such as Zoro's bad sense of direction (though he is barely better). Luffy also likes to comically imitate his crew members, and sometimes even himself; despite nearly dying from being frozen by Aokiji, he covered himself in flour and hopped while frozen in a pose to imitate the experience.
His level of trust and friendship with his crew is so high that he would even offer them a chance to eat the Mera Mera no Mi, which once belonged to his beloved foster brother, while the thought of it ending up in the stomach of some stranger was unbearable.
The Straw Hat
Luffy has a very bizarre relationship with his signature Straw Hat. The original owner was Gol D. Roger himself as told by Silvers Rayleigh. Eventually, it was given to Shanks, who passed it down to Luffy after saving him from a giant Sea King, on the condition that he take care of it, never lose it and only return it when he became better than Shanks. The hat cements Luffy's promise to become King of the Pirates and has been with him for over ten years. Subsequently, it has been repaired several times (mostly by Nami). In the beginning of the series, Luffy let people hold the hat during battle for fear of losing it, and whoever held it was considered to have his highest trust and respect. As his fighting style got better, he added a string and kept his hat on.
The straw hat has become an identifying marker for him by his enemies, to the point where his nickname became "Straw Hat Luffy" and his crew the "Straw Hat Pirates". Luffy is almost never seen without it, even when sleeping or fighting. His love for the hat is so strong, he is willing to kill anyone who tries to damage it, and during the fourth movie he actually cried a small waterfall when it went missing.
The first crew mate to join the Straw Hat Pirates was Zoro, a bounty hunter who decided to serve under Luffy as a pirate after he saved his life from a dishonorable death at the hands of a corrupt Marine, but vowed if Luffy ever got in the way of his ambition, he will kill him. Later in the series, they have developed a very close bond which is underlined by their tremendous amount of trust and respect for one another, to the point where Zoro is willing to die for Luffy's dream to become Pirate King and sacrifice his own dream of becoming the world's greatest swordsman. Though, he still hints at Luffy needing to uphold his duties and capabilities as captain, such as when he jokes that if Luffy were not at least able to use Haoshoku Haki, he'd have to step down as captain of the crew.
In times of trouble, Zoro has also served as an adviser to Luffy as to what course of action they should take. This is best illustrated during the events at Water 7 when Luffy was initially willing to have Usopp rejoin straight away, only for Zoro to explain what that would mean for the crew. Later in the New World Zoro was also the one to realize Luffy's recklessness would have to stop, going out of his way to reprimand his captain for behaving that way and making it clear they needed to take things more seriously in order to survive. 
Though she respects him as a captain, Nami often scolds Luffy's airheadedness, but he never gets angry at her, even when she manipulates him. Luffy also has no problems taking orders from her when it comes to the navigation of the ship. During the early days, Nami was the one Luffy entrusted his hat to during battles, showing a rather powerful trust between the captain and his navigator. Despite the slight conflict occurring because of his recklessness, she has deep trust in him and views him a great source of strength and comfort. She fell sick just prior to the Drum Island Arc, and without a doctor on board, Luffy desparately tried to help Nami the only way he knew how. He consistently stayed by her side, and attempted to get her to smile, becoming sad when he wasn't successful. When it was determined that the only way to get her treatment was actually climbing the Drum Mountains by foot, she implicitly trusted Luffy to get her there safely.
Even though Nami betrayed him when she stole their ship and treasure during the chaos at Baratie, Luffy never changed his opinion of her, insisting that she become the navigator in his crew. Oddly, he seems to place the most trust in her out of all of his crewmates - after learning from Johnny that he witnessed Nami killing Usopp, he refused to believe him, even going so far as to threaten him with a beating for "lying". In a similar situation in Whiskey Peak, where he was told that Zoro had killed and hurt the people who fed him, Luffy outright attacked him, even though that information came from an unreliable source (unlike the case with Nami).
Luffy's relationship with Usopp is perhaps the closest example on the ship of a sibling relationship because of their similar pasts and fun loving mindsets; despite his fears, Usopp at times finds the strength within himself by following the example set by Luffy and the rest of the crew. When he exclaimed that he was good with cannons, Luffy immediately made him the gunner of the ship. Usopp and Luffy are also destined to cross paths with the Red Hair Pirates in the future in some manner; Luffy to reunite with Shanks, and Usopp with his father. When Usopp left the crew, Luffy and Chopper were the most depressed about the event, but also joyously accepted him back after he apologized and begged to rejoin the crew. Usopp was also seen entrusted with his straw hat during one the Davy Back Arc, where he was using an afro, instead of his straw hat.
He adores Sanji's cooking, especially meat, dropping anything he's doing for a meal despite Sanji's claim that he puts considerably less effort into Luffy's food than the meals he prepares for the women. Sanji is also usually the one who has to "discipline" Luffy whenever food is stolen. Despite this, Sanji put his life on the line for Luffy's sake when Bartholomew Kuma had them weakened. Before Sanji became part of Luffy's crew, he stated that Luffy's dream was foolish, but acknowledges that his own dream is foolish as well. Though Sanji finds Luffy stupid at times, there is an underlying and often unspoken understanding that Sanji has great respect for Luffy, his ideals and his dreams. The fact that Sanji aspires to find "All Blue", which is similar to Luffy's dream to find the "One Piece", might add to this reason.
After the two year timeskip, after they reunited, once Sanji learned he was sent to Amazon Lily while the latter was surrounded by Okama's for two years resulted in Sanji becoming deeply jealous and angry with Luffy's situation resulting in Sanji sulking greatly afterwards.
Tony Tony Chopper
Chopper, as the youngest of the crew, often joins him and Usopp in singing and fooling around, and he credits Luffy for helping him find the courage to go on adventures. Chopper also often tends to jump after Luffy whenever his captain starts drowning, despite also being unable to swim due to having eaten a devil fruit as well. Luffy has deep faith in Chopper's doctoring skills, as when he explained that the "candy" that the giant children were eating was in fact a dangerous drug, he broke a promise with one of them to bring some more "candy".
Luffy and Nico Robin first began as enemies, but after Robin saves his life in Alabasta, Luffy grows to trust her more deeply which he shows by allowing Robin to join his crew without any reluctance. Robin is especially grateful to him for taking her in despite the risks it involved, as well as for pursuing her all the way to Enies Lobby and directly opposing the World Government. At Water 7, Luffy reveals that he is very impressed by Robin's intelligence when he is talking about her with the mayor Iceburg. As such, Luffy always turns to Robin for explanation whenever they encounter an unfamiliar person, place, or thing. At first she joined the crew because Luffy had saved her life when she wished to die, and had nowhere else to go, but eventually all of the crew members became important to her personally. Out of all the crew members, Robin is the most tolerant of Luffy's silly behavior, and actually finds him amusing. Robin is also one of the few members of the crew who unquestioningly follows Luffy into any dangerous adventure he wants to embark on.
Luffy initially didn't like Franky, with the latter's robbery of Usopp, despite Luffy and Usopp not being on the best of terms themselves. This led to his distrust of Franky for a long while, before he eventually came around to the shipwright during the Enies Lobby Arc and Franky's eventually joining the Straw Hat Pirates. He is always amazed by Franky's building talent, and is often in awe of Franky's cyborg enhancements and modifications, a running gag among many males throughout the show. He also deeply respects him as a man after he was willing to show his genitals to everyone without shame and begging Robin not to rip them off, so he would still be a man when he joins the crew. After the timeskip, with Franky looking and acting even more robotic, he has only become even more amazed.
Upon hearing Ace's Mera Mera no Mi has resurfaced and was a grand prize in the Corrida Colosseum, Luffy offered Franky to eat it, showing a great deal of trust and friendship, though Franky refused due to not wanting to lose his ability to swim.
Luffy came to almost immediately befriend Brook up their meeting, even despite the rest of the Straw Hats distrusting and outright refusing Brook, whether due to the initial mysteries behind his form or simply his personality. Luffy's admiration and eventual trust for Brook was cemented in his offering Brook a place in his crew, Luffy's self-considered family.
As the musician of the crew, Brook is often requested by Luffy to perform a song and will often join Luffy, Usopp, and Chopper in immature antics. Luffy had always stated that he wanted a musician in the crew, so Brook's job is very important to him. Brook often appears to enjoy Luffy's child-like antics and sometimes would even reinforce his humorous behaviour. This relationship is strengthened by the fact that Brook was part of the Rumbar Pirates, the crew that were such good friends with Laboon, and promised to meet up again.
Monkey D. Dragon
Luffy has discovered that Dragon the Revolutionary, the most wanted man in the world, is his father. The two have yet to talk to each other. In fact, their only meeting was when Dragon rescued Luffy from being captured by Smoker in Loguetown, and the only thing Luffy said to him was "who's there?" while being pinned headfirst to the ground by Smoker. It is highly probable that Dragon cares for his son's life because he saved him in Loguetown and he always looked towards East Blue where his family lived. Dragon seems to expect great things from Luffy, much like his grandfather. However, unlike Garp, Dragon seems to be in favor of Luffy's decision to lead his own crew as a pirate, although he believes they will meet someday. Luffy was unaware of who Dragon was before he was told by Garp and did not understand what the revolutionaries are capable of doing to the world when told about it by Ivankov. So far Luffy has not mentioned anything about how he feels toward Dragon and his ideals, but he is fine with people knowing that he is Dragon's son.
Portgas D. Ace
"Fire-Fist" Ace and Luffy were very close to each other. They grew up together and fought every day, with Ace always winning even though Luffy had eaten a Devil Fruit. Luffy displayed no grudge against Ace for always winning, but instead boasted that he could win now (though he appears to still acknowledge that Ace is still the stronger of the two, he proclaimed during the war in Marineford that he will eventually surpass Ace one day). Despite the battles they fought, Ace was protective of Luffy from Garp's abusive nature even going as so far to insult him to stop abusing Luffy. As for Luffy, this protective streak is reciprocated, leading to him embarking on a one-man rescue mission to extract Ace from captivity in the one place regarded as the most secure prison of the world, Impel Down, after hearing of Ace's capture and subsequent imprisonment there. However, while they are loving brothers to each other, Luffy always made Ace angry and worried by doing reckless things. As such, Ace readily believed Boa Hancock when she told him that Luffy had broken in to the prison. Even near his death, Ace grew angry with Luffy's reckless infiltration of Impel Down, while the endangered Luffy was worried about Ace's safety so much he had even snuck in the world's greatest prison, lost 10 years of his life, and even risked his arms to attack Magellan.
Luffy's devotion and love for his brother were shown to extremes when he not only took on every Marine stationed at Marineford, but the three Admirals themselves, showing that nothing would stand between him and saving his brother, not even three of the most powerful Marines around, and even shouting out loud he would save Ace even if it killed him. While Ace regarded Luffy as his brother and even acted like it, it was revealed moments before his execution that Ace was a child of Gol D. Roger, and that he chose his mother, Portgas D. Rouge's surname, which makes them brothers through adoption. A flashback shows Luffy and Ace first meeting as young children, which means that Luffy was aware of this fact. When this happened, Luffy already had his signature straw hat and the scar under his left eye, which means it was after Shanks gave his straw hat to Luffy and left the Foosha Village. He had also gained his devil fruit powers by then, which happened when he was 7 years old. It is revealed in a flashback that Luffy was sent to live with Ace and his guardian Dadan after Shanks left, since Garp thought that living in Foosha Village had somehow made Luffy "too soft". Ace was quite hostile to Luffy at first, even spitting at him before they were introduced to each other. Luffy, however, constantly tried to make Ace his friend, following him everywhere and trying to make up.
Eventually, thanks to the "Sabo Incident" Ace mentioned before he died, Ace grew fond of Luffy and they officially became brothers. Sometime after meeting Ace he managed to find out that Ace was the son of Gol D. Roger. Though many were heartbroken when Ace died, none took it harder than Luffy; Luffy was so devastated that he suffered a mental collapse and became unresponsive to his surroundings, and would have been killed by Akainu if others had not defended him. Jinbe speculated that this comatose phase was a way for Luffy to defend his mind from the impact of the loss, and worried about how Luffy would act when he woke up. Indeed, when Luffy did wake up, all he could do was scream in agony and cry and wish it was all a nightmare, and that he would wake up soon. The loss of his brother also had a crucial impact on Luffy, leading him to think that he was not worthy of becoming the Pirate King for the first time in his life. He only came out of his depression after Jinbe made him realize that Ace had entrusted Luffy's safety to his crew. After the two year timeskip, Luffy has fully gotten over his grief as he was able to talk about Ace's death freely, although his hatred for the man who killed his brother apparently still remains. Nonetheless, Luffy accepts Ace's fate, but also finds comfort in the fact that Ace truly believed he could become the Pirate King.  Donquixote Doflamingo would later take possession of Ace's Mera Mera no Mi, an item which the Shichibukai was certain would draw Luffy to him, adding that Luffy would never allow anyone to gain the powers that once belonged to his beloved brother. Indeed, Luffy showed surprise when he heard of the fruit being handed out as a prize in a tournament and, not wanting it to go to just anyone, entered the tournament to win it. He was, however, fine if one of his crew members ate it, as he offered Franky the fruit. He has shown that he doesn't like it when Ace's death is made fun of as when Don Chinjao said that it was a wise move of the Marines to 'cleanse that demonic bloodline two years ago'. This angered Luffy to the point that he struck Chinjao with a Gomu Gomu no Thor Elephant Gun.
Monkey D. Garp
Though the two of them get along fine, Luffy is utterly terrified of his grandfather Garp. This is due to the extreme training he was put through in his younger years in his bid to make Luffy a Marine, as well as Garp's tendency to punch Luffy to discipline him. Garp had high expectations for Luffy, but to Garp's dismay, Luffy did not share his grandfather's plans for his future. However, Garp respects Luffy as a great person, even if he is a pirate. He often brags about Luffy to his superior Sengoku, laughing whenever Luffy does something audacious and is prone to saying "That's my grandson" much to Sengoku's exasperation. When Sengoku was talking with Garp and Kuma, Garp said that Luffy is not the type of person to brag about defeating someone, arguing that Bartholomew Kuma did not need to kill Luffy to keep Moria's defeat a secret. When Luffy entered the battle of Marineford, Garp recognized him and looked shocked and horrified at the sight of his grandson entering the fearsome battle. Later, as the battle rages on, Garp merely looks resigned as his grandson furiously makes his way to the execution platform. When Luffy came close to the platform, Garp stands in his way in the name of his Marine duties. However, in the end, Garp chose family over his duties as he allowed Luffy to hit him and reach the execution platform to save Ace. He also tried to attack Admiral Akainu when Ace was killed by the admiral and Luffy was on the verge of being killed as well, but was stopped by Sengoku. As Garp has resigned from the Marines, he and Luffy are no longer enemies by law.
The mountain bandit, Curly Dadan, is Luffy and Ace's foster mother. She had been blackmailed by Garp into taking care of them, and did not seem pleased with having Luffy as her surrogate son, due to being already occupied with the troublesome Ace. Luffy, in turn, did not seem to like the Dadan family anymore than they liked him, due to his run-in with the bandit Higuma. However, as time passed, they came to care for each other, with Dadan coming in to save Luffy from Bluejam, and Luffy worrying for Dadan's safety. Luffy states that he hates bandits but he likes her.
Sabo was never an actual member of Luffy's family, but he, Luffy and Ace shared a drink making them official brothers and establishing the deep bond between the three. They seem to be reasonably close, though not as deep as Ace and Luffy. This is however most likely simply because they did not spend as much time together with Sabo being taken away and they never saw each other again for 12 whole years. He still had a tendency to defend or save him when they were children hunting together. Even though when he first met him he wanted to kill him for discovering their plans. According to Luffy, when they were young, Sabo was a nicer brother to him than Ace. After Sabo and Ace fought together against Porchemy to save Luffy's life they became friends. At this point they were seen after different events of stealing and hunting. Sabo was seen being taken back by his father, who recently revealed that he was the son of a Goa Kingdom Noble. They show a relationship of trust and love since he gave up and returned with his father so that Luffy and Ace would be safe from the hired pirate Bluejam. When Sabo's apparent death was reported by Dogra, Luffy cried all night until he fell asleep, showing the genuine love he had for his elder brother. Luffy only snapped out of this sorrowful moment when Ace told him to live proudly, as Sabo wanted. When Sabo and Luffy were reunited after twelve whole years, Luffy began joyfully crying for a great deal of time after finding out his remaining brother was alive and well. In a way, Sabo is one of the earliest contributors to the moulding of Luffy's personality as a free spirit.
It is notable that Luffy has connections to some of the most powerful organizations or people, mostly through his extensive and famous family. His known family alone has him connected to powerful members in the Revolutionary Army, Marines, and Whitebeard. Besides his family, he has Shanks, Rayleigh, Boa Hancock, Jinbe, Coby, and Helmeppo, who connect him to another Yonko, Shichibukai, and again the Marines. As the Kingdom of Alabasta is an affiliate nation of the World Government, through Vivi (and by extension, Cobra), he may also possess some influence there. Therefore, of the reigning World Powers, the Gorosei is the only organization to which he is not somehow amicably connected.
Luffy befriends most of the civilians he meets on his journey, who normally fear him for being a pirate but hold him in admiration by the time he moves on to the next adventure. He can be naïve at times and is quick to befriend people, often calling people whom he has known less than a day his friends and being willing to go as far as necessary for them. During his journey, Luffy saved or freed civilians from the tyrannical clutches of villainous antagonists on several occasions. Luffy befriended many civilians from Shells Town, Orange Town, Syrup Village, Cocoyasi Village, Drum Island, Alabasta, Skypiea, Water 7, Fishman Island, and Dressrosa.
Luffy shares a strong relationship with Shanks, the pirate who saved his life twelve years ago in his hometown, and looks up to him as his role model of an ideal pirate. Shanks and his crew are the ones Luffy proclaimed he would beat as they were leaving Luffy's hometown. Luffy will often defend Shanks when others insult him and was relieved to hear from his grandfather that Shanks and his crew were okay. Part of Luffy's dream is to return the hat Shanks gave him when he becomes a great pirate. Shanks, while frequently making fun of him as a child, has remained informed of Luffy's activities and is proud that he has become a pirate. Luffy has since worked diligently on keeping that promise and is infamously known as "Straw Hat Luffy". While discussing taking down the Yonko with Trafalgar Law, Luffy indicated a desire to defeat Shanks as well; echoing his promise to one day form a crew strong enough to defeat the Red Haired Pirates, though he wants to save him for last.
Red Hair Pirates
Twelve years ago Luffy seemed to be friends with the Red Hair Pirates. This extends to two years ago when Benn Beckman stopped Kizaru from attacking Luffy. Lucky Roo seemed fond enough to want to see Luffy again after rescuing him at Marineford to the point he asked Shanks if he wanted to see him after 10 years.
While Coby, the first person Luffy met on his journey, acknowledges that as he is a Marine, they will inevitably have to fight. However, they consider each other friends, as Luffy helped Coby muster the courage necessary to become a Marine. Coby holds great respect for Luffy, and he promises to always be a friend, though his dream - becoming a Marine - is opposite to that of Luffy's. Later on, having met on Water 7, Luffy inspired Coby to pursue his dream of becoming a Marine admiral. Despite having clashed during the war, it appears not to have damaged their friendship, as Coby still admires Luffy's strength.
After entering the Grand Line, Laboon was the first thing the Straw Hat Pirates saw. Launching the cannon in the hopes that it would slow them down, Luffy, instead, hit Laboon. After saving him from Mr. 9 and Miss Wednesday who were trying to use Laboon for food, Crocus explained to Luffy why Laboon would slam his head into the Red Line. Luffy, in an effort to give Laboon a renewed sense of hope, picked a fight with the whale by jamming the Going Merry's mast into the whale's head. After the battle (which Luffy called a draw), Luffy promised Laboon that he would return to see him, under the guise of wanting a rematch, moving Laboon to tears of joy. As a sign of the promise of the future rematch, Luffy paints the Straw Hat Jolly Roger on Laboon's head, commenting that the insignia would be washed away if Laboon hit Reverse Mountain further. This prevents him from slamming against the mountain anymore. The Straw Hats then depart in good spirits for Grand Line.
Luffy is good friends with Nefertari Vivi, who was with them all throughout the Alabasta arc, and he even considers her an honorary Straw Hat crew member. Whenever she sees Luffy doing something that might compromise the crew's safety, even when he means to help, she reminds him of a leader's responsibilities, and she holds Luffy in great respect for helping save Alabasta. She was not shocked that Luffy took Nico Robin into his crew despite her being Vivi's enemy in the past (showing trust in his judgment), and she did not show any prejudice about Luffy being the son of the world's worst criminal.
Mr. 2 Bon Kurei
Luffy became good friends with Bentham after he apologized for causing them trouble in Alabasta, and distracted the Marines so the Straw Hats could escape. Bon Kurei went as far as to give his life away to save Luffy and other prisoners by posing as Magellan and ordering the opening of the Gates of Justice during the Impel Down Arc. While he was later determined to be alive, Luffy is unaware of his friend's condition.
Skypieans and Shandia
Defeating the "God" of Skypiea and freeing its people, as well as granting the Shandia back their homeland, ringing the golden bell, and saving Angel Island, Luffy and the rest of the Straw Hat Pirates have become heroes to the people. They even offered the broken column to their saviors. With peace restored to the land many hope that the Straw Hats will visit again. Many were also disappointed that they never got to say good bye and rang the golden bell instead. Aisa seems to hero worship Luffy as a role model, and Gan Fall also compares Luffy to the Pirate King Gol D. Roger.
Luffy also seems to have developed a positive relationship with Trafalgar Law and his crew, as they braved the Whitebeard War and the attacks of the Marine admirals just to save him. Although seeing that they are both Supernovas, and therefore rivals, there may be some ulterior motive behind Law's decision to save Luffy. While on the other hand, Law has been shown to respect Luffy, and could quite simply have come to save him because of that respect. When Luffy met Law on Punk Hazard, Luffy was happy to see him again, not knowing Law's intentions. Luffy stated, with a happy smile on his face, that he and Law will be enemies if he's going after the One Piece too, but he is grateful nonetheless. It also seems like Luffy cannot pronounce "Trafalgar" properly and calls him "Tora-man" (トラ男 Tora-o?) instead. Luffy was visibly surprised when Robin revealed that Law became one of the Shichibukai during the time-skip. When Law helped save Nami, he proposed an alliance to Luffy to take down one of the Yonko. To the surprise of their crewmates, he accepted after being told that they would be taking down Kaido; saying he intended to take them all down. He appears to trust Law to go along with this plan of action. When Law was shot by Doflamingo, Luffy showed a lot of concern for his ally. After that, when the North Blue pirate was kidnapped by the Shichibukai, Luffy stated his desire to rescue him.
During Law's desperate struggle against Doflamingo, it was shown that Law thinks highly of Luffy and his crew, saying that they are capable of performing miracles. Law later stated that if Luffy was to be defeated by Doflamingo, he would allow himself to be killed as well, since they are in an alliance together. He also said that the fight between Luffy and Doflamingo is his fault, but Robin corrected him, saying that Luffy would not enter a battle with no personal reason.
Ever since Rayleigh had heard about Luffy from Shanks he had wanted to meet him face to face. When Luffy found him on the Sabaody Archipelago, he was really excited about hearing stories about Gol D. Roger. The more they talked, the more amused Rayleigh felt as he compared Luffy's demeanor to his old captain. He, like Shanks, has very great expectations for him. After the war had ended, he swam across the Calm Belt to reach Amazon Lily where Luffy had been recuperating from his injuries and from losing Ace. From there, he helped Luffy break into Marine Headquarters again with Jinbe in order for him to send the secret message to his crew. Rayleigh also mentored Luffy on how to master all three different forms of Haki that he possessed. After the 2 year timeskip, it is apparent that both of them became close from their training together as before heading to his ship, Luffy yelled towards Rayleigh with a big smile "I'm gonna do it, I'M GOING TO BE PIRATE KING!", with Rayleigh donning a smile with tears in his eyes. Rayleigh himself later proudly proclaimed Luffy as his pupil to the Marines and kept them busy to prevent them from interfering in Luffy's departure. While Luffy set sail Rayleigh seemed to be comparing his late captain Roger and Luffy, claiming that destiny is slowly but surely taking shape and that Luffy has become a man well fit to wear the Straw Hat, which originally belonged to Roger. He also said that it might be worth living a little longer.
He also has a very friendly relationship with the entire population of Amazon Lily despite their initial hostility towards him. But after Luffy gained Boa Hancock's friendship, it seems every single Kuja practically worships him, as they had never seen a man before. They even went as far as selling "touches and pokes" of Luffy for 20 gold pieces each and most of them affectionately refer to him as "Luffy-sama".
Luffy managed to befriend the Gorgon Sisters, despite their previous attempts to kill him for seeing the mark on Shichibukai Boa Hancock's back, which the other two sisters also have. The mark was of the World Noble, proof that they were once a slave to them, and they would have rather died than show the mark to anyone. During a fight with Hancock's sisters, when Boa Sandersonia's mark was about to be revealed, Luffy served in preventing everyone present from viewing it as a form of respect to his opponents, claiming that their secrets have nothing to do with their fight. This sparked up past memories in Hancock, and she then revoked her decision to eliminate him. Upon further testing his selflessness, she reveals their past to him, and Luffy forgives them, showing that he only hates the Celestial Dragon who did all of them wrong, earning their friendship and Hancock's love. He has come to greatly appreciate Hancock in return, as she helped him in the two major instances of helping him break into Impel Down and giving him the key to Ace's seastone handcuffs. However, while Luffy does not have the same romantic feelings towards Hancock that she feels towards him, he has shown that he genuinely cares for and appreciates her. During his fight with Magellan, when the warden stated that he would have Luffy tell him how he managed to break into Impel Down, Luffy protected Hancock by declaring he would not tell Magellan even if it killed him. He later showed his gratitude by hugging her and remarking afterward that she had "saved his ass" twice, both in helping him break into Impel Down and giving him the key to Ace's seastone handcuffs. After the two-year timeskip, Hancock mentioned that she's a thoughtful woman suitable to be a great wife for loading the ship with Luffy's favorite foods. Luffy replied that he was grateful to her for bringing food for him, but he wasn't going to marry her. Regardless, Luffy replied that he wishes to see her again sometime in the future.
While initially assisting Luffy only to protect and rescue Ace, the ex-Shichibukai Jinbe grew so fond of Luffy that he proclaimed while fighting Akainu at Marineford that he would gladly lay down his life to protect Luffy. After escaping the ordeal, he stayed with Luffy on Amazon Lily while he was recovering. It was Jinbe who also brought Luffy out of his self-pity and doubt. The fishman made Luffy realize that even though Ace had died, he still had his own pirate crew. As Jinbe departed from the Kuja ship, he and Luffy expressed the desire to see each other again in two years. Luffy tells Keimi of this desire, only to be disappointed when he finds out that Jinbe had to leave Fishman Island. However, before he left, Jinbe did leave a message for Luffy with Prince Fukaboshi.
When they met after two years Jinbe was happy to see him again but surprised he had not received his message. As he himself stated, he has the deepest gratitude for Luffy and his crew for stopping Arlong. He also wanted to apologize to them for Arlong, since he was the one who let Arlong go to the East Blue. Despite the mutual respect between them, after Luffy announced his desire to fight against Hody Jones to save his crew, he informed Jinbe that if he wanted to stop him, he would have to fight him. They eventually reached a compromise and formed a united front to combat Hody Jones and his crew. After the battle of Fishman Island, in which Luffy lost a large amount of blood, Jinbe offered his blood for the transfusion. Upon recovering, Luffy asked Jinbe to join his crew. While happy to have been asked, Jinbe declined the offer, stating he has other business to take care of first, but said when all that was done and they meet again, if Luffy and his crew still wanted him to join later, he promised he would join then. Luffy and all the crew members show they want him to join.
Luffy has on numerous occasions been aided or befriended by members of the Revolutionary Army due to being Dragon's son. In Impel Down, he befriended Emporio Ivankov and Inazuma. Before directly encountering him, however, Ivankov and all of his Okama followers were already aware of Luffy's status as not only a pirate but Impel Down's first-ever intruder through the Den Den Mushi surveillance systems within the Great Gaol, and he unintentionally achieved a celebrity status within New Kama Land as a result. Ivankov helped save Luffy's life with his healing hormones because he was moved by Luffy's selflessness, as Luffy begged that Bentham be saved even while being on the verge of death himself. Once they learned of his connection with Dragon, Ivankov determined himself to ally himself with Luffy, and protect the young pirate's life as best he could. Ivankov and Inazuma both aided Luffy in the breakout of Impel Down and assisted him in rescuing Ace at the Battle of Marineford. Upon the war's end, they snuck aboard the Marine ship that Boa Hancock took over. Ivankov then left Luffy in Jinbe's hands and then left with his Newkama followers to return to Momoiro Island as well as saying that he would like to meet Luffy again.
He gained the assistance and admiration of all of the Whitebeard Pirates and allies, even Whitebeard himself, in his quest to save Ace. After seeing the lengths to which Luffy would go to save Ace, Whitebeard even remarked that he would not forgive Marco if he let Luffy die. Soon after, he assigned his crew and allies to back up Luffy after witnessing him unleash his Haki. After the death of Ace, the whole Whitebeard Pirates crew protected Luffy, as if he were Ace, claiming that he is all that is left of Ace's spirit.
Some time after their arrival, the Straw Hat Pirates became criminals of Fishman Island except for a few friends due to suspicion of kidnapping mermaids, Madam Shyarly's prophecy of Luffy destroying Fishman Island, and then Luffy's crew taking over Ryugu Palace when the Neptune Army attacked them. However, things changed after Hody Jones launched his coup d'état and was on the verge of executing Neptune. Rather than watching their king die, the civilians were willing to see Shyarly's prediction come true. During the ordeal, the Straw Hats were able to gain the civilians' trust after Luffy thwarted Neptune's execution per Shirahoshi's pleas and when the crew was seen fighting alongside Jinbe. After saving Fishman Island from the New Fishman Pirates, Vander Decken IX, and Noah, Luffy and his crew were cleared of the kidnapping charges when the mermaids were found and the Straw Hats were hailed as heroes for their efforts in saving the island from destruction. However, when Luffy was suffering from critical blood loss, the civilians did not do anything to help him due to their laws, but they rejoiced when Jinbe volunteered to be the blood donor. After a huge party in the Straw Hats' favor, Luffy discovered that while Fishman Island was protected by Big Mom, she would not hesitate to destroy Fishman Island if she did not receive her monthly 10 tons of candy. Luffy then took responsibility for the missing candy to protect Fishman Island again. When negotiations of treasure instead of candy failed, Luffy declared that he would defeat her in the New World and claim Fishman Island as his territory.
Fukaboshi did not show resentment towards to Luffy or his crew when they arrived (even though it was illegally). In fact, he only wanted to find him in order to deliver a message from Jinbe. When Luffy was accused of kidnapping mermaids and prophesised to destroy Fishman Island by Madame Shirley, he begun to raise doubts of both accusations. Finally, when he discovered that Hody Jones hated humans simply because he was raised to, he begged Luffy to, "set everything to zero." Luffy obliged on his request, saying that they are friends of course.
Luffy formed a friendly relationship with Princess Shirahoshi after saving her from an axe thrown by Vander Decken IX and after she learned that he saved her beloved pet shark, Megalo. Once Luffy learned that Shirahoshi had been locked in Hard-Shell Tower for ten years to keep her safe from Decken, he stated that it must have been really boring for her. Luffy then offers to take a walk with her outside the castle with him serving as her bodyguard so she could see the world outside her tower while protecting her from Vander Decken IX. Even though Luffy and Shirahoshi do get along, Luffy gets annoyed at her tendency to cry. After seeing how fragile Shirahoshi's personality is, Luffy bluntly called her a crybaby and a weakling. This seems to parallel how Ace and Luffy's relationship were as children. Shirahoshi, however, does not show any resentment towards Luffy for calling her names. After seeing how Shirahoshi was able to honor her mother's final wish for so many years, Luffy acknowledges that she is not as weak as he originally thought. He then calls her "Weakhoshi" since he still considers her a crybaby.
As one of the pirates who belonged to the Worst Generation, Brownbeard originally hated Luffy. Luffy on the other hand had no clue who Brownbeard was when the two first met. Initially enemies due to Luffy and his crew opposing his "master", Brownbeard did not trust them and resented them for capturing him. However, Luffy seemed to respect Brownbeard's admiration for Caesar. When Luffy discovered that Caesar betrayed Brownbeard, his hatred for the scientist grew and he resolved to save Brownbeard from being killed by his own followers under Caesar's command. When the conflict was resolved, Luffy thought it was a shame when Brownbeard decided to turn himself in, even calling the former pirate his friend.
Luffy met Bellamy back on Jaya and, after the latter mocked Luffy for chasing his dreams and believing in things like One Piece and Sky Island, Luffy chose not to fight back and let Bellamy and his crew beat on him, mirroring what Shanks did to Higuma. However, after Bellamy assaulted Cricket and stole his treasures, Luffy returned to fight him. As Bellamy continued to ridicule him on his dreams, Luffy returned the favor from earlier and brutally pounded Bellamy in the ground with one punch.
Two years later, Luffy was shocked to see him again and surprised that Bellamy no longer holds any ill towards him and will not laugh at him. During his fight in Block B Luffy even cheered for him and they later had a friendly talk. Bellamy was even reluctant to assassinate Luffy per Doflamingo's orders. During the Bird cage game Luffy declared Bellamy a friend after seeing him so horribly beaten by Doflamingo after all the admiration the latter had for him. After Doflamingo released Bellamy from his control, Bellamy refused to betray his own principles and asked Luffy to fight him one last time. Though Luffy tried to talk him out of it, he reluctantly punched Bellamy in the ground in a similar manner at Jaya. With his last thoughts, Bellamy thanked Luffy for calling him a friend.
Corrida Colosseum Gladiators
Luffy has been on good terms with Rebecca after she shared the story of Kyros with him when he took an interest in his statue. Rebecca was thankful for Luffy defeating Spartan and was impressed with his performance during the Block C battle royale. Even though she tried to kill Luffy to better her chances of getting the Mera Mera no Mi in order to protect the one she cares about, Luffy did not hold a grudge against her and was still thankful for her buying him food. Afterwards, Rebecca opened up to him. In turn, Luffy considers her a nice person and was angry at the audience for throwing horrific insults at her due to her lineage. When Doflamingo unleashed the Birdcage to conceal Dressrosa, she became a target to his game, which caused Luffy to worry about her. Luffy promised Rebecca that he would repay her by defeating Doflamingo and when she asked Luffy if he can defeat Doflamingo, he proclaims he can since he's going to become King of the Pirates. After defeating Doflamingo, she cried in tears when Luffy won and was by his side when he became unconscious after the battle. Even after finding out his real name, Rebecca still calls him by his gladiator name "Lucy". Luffy cares for Rebecca, he was not happy with Kyros's decision to stay away from her, so Luffy ran to the palace in spite of being chased by the Marines asking her if she is ok with her father's decision. After Rebecca replied she is not, Luffy took her close to where Kyros is. This seems to parallel how Luffy felt when he was a boy where he and Ace were forced to stay away from Sabo and couldn't free him due to their social class.
Because Monkey D. Garp crushed his pointy head and robbed him of the means to acquire a certain treasure, Chinjao developed a hatred not only against Garp but also those in his bloodline. At the Corrida Colosseum, Chinjao originally tried to take his grudge out on Luffy. Ironically, when Luffy defeated him, he inadvertently returned what Garp took away by restoring his pointy head, gaining his gratitude. Afterwards, Chinjao's grudge against Luffy and his family was lifted and he later joined forces with Luffy to defeat the Donquixote Pirates.
Cavendish harbors a deep-seated resentment of the Supernovas, including Luffy, for stealing the spotlight from him. At first, Cavendish was friendly and sociable to him since Luffy was under the guise of "Lucy". However, right after learning his true identity, Cavendish immediately turned hostile and became hell bent on killing Luffy with his own hands. This hostile nature changed when Usopp helped in his transformation back to human from a toy, even to the point where he tells Luffy that he'll take down Doflamingo to pay the debt.
Two years ago, in Loguetown, Bartolomeo witnessed Luffy survive execution at the hands of Buggy the Clown. From that moment forward, he followed all of the Straw Hats' adventures, growing more and more delighted at the crew's escapades. Bartolomeo feels great admiration for Luffy and his crew, and it is shown he will do anything to the point of cutting off a man's tongue for badmouthing Luffy. He was even willing to sacrifice his own life for the Straw Hats.
Because Luffy (while as Lucy) was gaining such attention in the Colosseum with his amazing feats, the commentator Gatz became a huge fan of Luffy rooting for him to win the competition. During the fight against Doflamingo, Gatz came to Luffy's side when his Gear Forth wore off and protected him from Doflamingo's rampage long enough with various gladiators to give Luffy enough time to regain his Haki. Furthermore, he has a lot of faith in Luffy to the point he made a broadcast to the whole island that Luffy would defeat Doflamingo with one punch and save the kingdom. After Doflamingo's defeat Gatz tearfully proclaims Luffy to be the victor of both the fight and the savior of Dressrosa.
There are those Luffy have gain a certain acquaintanceship with, for one reason or another.
Though antagonistic towards one another earlier in the East Blue, Luffy's relationship with Buggy is overall similar to that of Buggy's relationship with Shanks: a friendly yet slightly antagonistic way. Though Buggy was a formidable opponent for Luffy when they met, now Buggy is nothing more than an annoyance to the Straw Hat captain, having barely noticed Buggy when he met him again in Impel Down. Buggy on his part tends to attempt to take advantage of Luffy's naivety for his own personal gain (though whenever Luffy responds with his usually kindness results in Buggy being very guilty). After learning who Luffy's father was, Buggy was deeply shocked realizing further why Luffy is such a trouble maker.
Bartholomew Kuma similarly came to the rescue of the Straw Hats on numerous occasions. In their first meeting, Kuma allowed Luffy's crew to escape from Thriller Bark, despite being ordered to kill them. This was likely due to his conviction as an officer of the Revolutionary Army. While it is not known what his intentions were in engaging the crew in battle, and forcing Zoro through an incredible test of endurance, it is likely that he meant to test their dedication to Dragon's son, and expose them to the terrifying power of forces in the seas ahead. In their second meeting, Kuma directly interfered with an assault by the Marines to save the crew with his teleportation powers. Finally, as his last act of free will, he had Dr. Vegapunk program him to protect the Thousand Sunny until its crew returned. The incredible lengths Kuma took to aid them has made him a savior of the crew. When also considering the army's care for Robin during the two years of separate training, it is likely that the Revolutionaries will prove to be powerful and dedicated allies in the future, despite Dragon's choice to have almost no direct contact with his son. However, Franky stated that while they owe a great debt to him, the next time they meet he will have become nothing more than a mindless killing machine for the government.
While Luffy has amass a large and diverse network of friends and allies, he has also made enemies and rivals out of some of the greatest figures and organizations of the sea as well over the progression of his voyage for various reasons, the three most prominent examples being they somehow hurt those he see as friends, they desire the title "King of the Pirates" or more recently due to his revealed heritage.
Naturally as a pirate, Luffy is an enemy of the World Government. However, they started taking him seriously after he surpassed every pirate in the East Blue, and even more after defeating Crocodile at Alabasta, even more when declared war on them by burning their flag and defeating the CP9 at Enies Lobby, and now they see him as a potential threat to the whole world when he is revealed to be the son of the Revolutionary Dragon, and that he survived the Whitebeard War.
Luffy has made enemies out of the Gorosei, which they consider Luffy both a trouble maker and a potential threat to the government after his victory over Crocodile. Because of Luffy's actions, the Gorosei view Luffy as a potential threat to the balance of the Great Three Powers, especially after learning of his relationship to Dragon.
Luffy has also made enemies of the World Nobles after punching Saint Charloss for shooting his friend, Hatchan. Luffy even stated that he hates the World Nobles while Hancock explained her past as a slave. During the Whitebeard War, Kizaru stated that the nobles have been clamouring for his arrest. Luffy's detestment to the World Nobles was added to his despisment for Doflamingo after the latter revealed he used to be one.
Luffy and his crew are major enemies of the CP9 agents for declaring war on the World Government and for them trying to kill Robin. Luffy originally thought of the agents he met at Water 7 to be good people, but once he saw them trying to frame them for killing Iceburg, destroying Galley-La Headquarters and forcing Robin to accompany them, Luffy became enraged by their actions and became enemies. Luffy viewed the agent Blueno an annoyance for standing in his way from getting to where Robin was, but thanked him for a good fight and helping him uncover his Gear Second. Spandam originally viewed Luffy as a weak pirate, but after his assault on CP9 and his crew winning and saving Robin, Spandam has developed a grudge against them. However, Luffy's biggest enemy of CP9 is Rob Lucci. With Lucci, Luffy holds a deep hatred for trying to kill him and his crew and all of Galley-La despite knowing them for years. Lucci even personally attempted to make sure Luffy's crew would not survive Enies Lobby by flooding the underground passage from where they all in hopes of Luffy losing everything for his own enjoyment. Lucci continuously mocked Luffy, stating he's too weak to defeat Enies Lobby and save Robin. However, Lucci is one of the strongest opponents Luffy has ever faced and forced the Straw Hat captain to push himself beyond his limits to defeat him. Regardless, Luffy stated he is glad to have met them, due to him having become stronger from fighting them.
Luffy also made a very dangerous enemy out of Magellan during his break-in at Impel Down. The fact that Luffy was the first to break into Impel Down was enough to infuriate Magellan. The chief warden severely poisoned Luffy during their first battle causing Luffy to lose ten years of his life span in a painful healing process. After realizing that Luffy survived his poison and had released more prisoners, Magellan did everything in his power to ensure that Luffy did not leave Impel Down alive. Even though Luffy did not manage to defeat Magellan in battle, he did successfully tarnish his reputation by escaping his grasp.
Even the Marines started to take him more seriously after he defeated the villainous Marine Captain "Axe-Hand" Morgan and several known pirates such as Buggy the Clown, "Pirate Admiral" Don Krieg, and Arlong the fishman. A 30,000,000 bounty was placed on his head after he had beaten Arlong and the Marines were cautious about Arlong's defeat because it had brought to question the worth of their units. This reward eventually becomes 100,000,000 after he defeated Crocodile, when the World Government deemed him a serious threat for defeating one of the Shichibukai. After the invasion of Enies Lobby, where they declare war on the World Government itself, the government raised the bounties of the entire crew; Luffy's was raised to 300,000,000, and to 400,000,000 after the Whitebeard War.
During his voyage, Luffy has had a few meetings with the Marines, from the not too serious looking return of Ironfist Fullbody (whom Luffy met first by the Baratie) and Captain Smoker of Loguetown, to Admiral Aokiji. While some are easy to defeat, Luffy has been unable to defeat Smoker or Aokiji due to their powerful Logia abilities, and has resorted to running away from Smoker when he encounters him.
During the Whitebeard War, Luffy made his biggest enemies out of the three Marine admirals. Kizaru was a major hindrance to Luffy's attempts to rescue Ace. He kept Luffy from his goal multiple times and even destroyed the original key to Ace's handcuffs. Kizaru also mocked Luffy for lacking in power to save Ace. Aokiji, who stated that Luffy chose the path of death himself, would have killed Luffy if it wasn't for Marco's interference. However, Admiral Akainu caused the most damage to Luffy, sending him into a mental breakdown by successfully killing his brother, Ace. Despite their incredible might that surpassed Luffy at the time, he did not show any fear whatsoever against an admiral, as he challenged Aokiji to a one-on-one fight, attacked a World Noble despite knowing the consequences, and attacked all three in an attempt to save Ace.
Luffy has a great rivalry with Smoker since the two met in Loguetown. Smoker is determined to capture him at any price. However, Luffy admitted that he likes him, and sees him as a good guy, as in Alabasta Luffy asked Zoro to save Smoker from drowning. In Punk Hazard, both had to put aside their rivalry to join forces and face Caesar Clown.
Luffy holds great hatred for Fleet Admiral Sakazuki for killing his brother Ace in the battle at Marineford. During the war 2 years ago, when Sakazuki was known as Admiral Akainu, this act brought Luffy into a mental breakdown, sending him into an unconscious state. The future fleet admiral proceeded to hunt him throughout the entire battlefield, swearing to end his life no matter what, despite Blackbeard attempting to bring down Marineford. True to his word, Akainu focused all his efforts on ending Luffy's life, which reached the point of dangerous obsession, as it took the combined efforts of Jinbe, Crocodile, and the Whitebeard Pirates just to protect Luffy from Akainu's relentless pursuit. Although managing to kill Ace, Akainu ultimately failed to kill Luffy after the intervention of Coby, and the arrival of Shanks. Nonetheless, after striking through Jinbe, Akainu managed to leave Luffy with an x-shaped scar on his chest, which seems to constantly remind him of his loss, evidenced when he touched the scar in anger upon learning of Akainu's promotion to fleet admiral. To this day, Akainu was the only enemy in the series who succeeded in completely breaking Luffy's spirit.
Luffy and his crew become Caesar's enemies after they stumbled on Punk Hazard. To ensure that word of his felonies does not become public, he ordered his underlings to eliminate the Straw Hat Pirates. Once the crew learns of the sinister experiments that Caesar has been conducting, they aim to capture him. Luffy did originally think of him as a nice person from what Brownbeard stated, however, after hearing from Momonosuke about his cruel treatment towards his men and how he does not care about what happened to the children, Luffy became enraged and more determined to defeat him. Caesar warned him that if he defeats him, Doflamingo and one of the Yonko will come after him by touching him, though Luffy retorts with an angry punch stating he has been taking on guys like that since he entered the Grand Line.
Despite his fearsome reputation, Luffy let Zoro face the Shichibukai and, after seeing Dracule Mihawk nearly kill Zoro, Luffy flung into rage but later was pleased seeing Mihawk let him live to surpass him. It appears Mihawk likes to keep tabs on Luffy and his crew due to the vast potential they posses. During the Whitebeard War Mihawk purposely fought Luffy to test him if he's worthy of the next age. However, to Mihawk's opinion, he views Luffy as a potential threat for the future due to his unique ability to make allies out of everyone he meets, even former enemies.
After seeing Crocodile and his Operation Utopia plan to destroy Vivi's kingdom, Luffy grew furious at the Shichibukai swearing to beat him up. However, Crocodile viewed Luffy as just another rookie who knows nothing of the world. Even after meeting him in Impel Down, Luffy initially refused to let him out of his cell and had not forgiven him for what he did. However, Luffy's view on Crocodile seems to have mellowed out somewhat, after he saved Ace and him from getting killed respectively. During their 3rd fight, Crocodile stated once Luffy learns what the seas are truly like, he would forsake his dream. Those words came to pass as after Ace died, Luffy believed he was too weak to be the Pirate King and only some encouragement from Jinbe and Rayleigh did he regain his fire.
Luffy is a major enemy of Gekko Moriah for trying to take his and his crew's and others shadows. That feeling is mutual, and they also seem to see each other as rivals, as they both aim to become the Pirate King. Like Crocodile, Moria viewed Luffy as an inexperienced rookie stating the he's no where near ready for the New World and would only lose everything due to his overconfidence. True enough, Luffy and his crew were utterly powerless to Kuma and were scattered across the world and trained for the next 2 years to grow ready for the New World. At the Battle of Marineford, Moriah was very displeased to see Luffy again and attempted to steal his shadow once more only to be repelled by Jinbe. Moriah was also the only Shichibukai to be shocked upon hearing that Revolutionary Dragon was Luffy's father.
Doflamingo originally thought little of Luffy, however, he did advise Caesar, Vergo and Monet to be vigilant of him and his potential. Furthermore, after discovering Doflamingo used Ace's fruit to lure Luffy to the Corrida Colosseum, Luffy refused to let anyone else claim it. He later became furious with Doflamingo for trying to kill Law and his cruel treatment towards the people of Dressrosa and promised Rebecca he would defeat him. His anger became both shock and fury after hearing Doflamingo reveal his past as a World Noble and stared angrily as the latter bragged how he murdered his father without remorse. His rage increased after being forced to defeat his former enemy Bellamy due to admiration of Doflamingo despite how he treated him. This fury further increased upon seeing Law unconscious and missing an arm thanks to his battle with Doflamingo.
Robin stated that the Pirate Alliance between the Straw Hat Pirates and the Heart Pirates would not be the sole reason he was fighting Doflamingo. This idea was supported when Luffy began activating his Gear Fourth, saying that Doflamingo's deeds are the reason of his fight with the Shichibukai.
East Blue Pirates
Luffy has made enemies out of many pirates during his journey to become the Pirate King. Before entering the Grand Line, the first pirate enemies that he met in East Blue include Alvida, Buggy, Kuro, Don Krieg, and Arlong. Luffy freed Alvida's cabin boy, Coby, and became the first man to ever hit her. Buggy mocked Luffy's dreams and became the first person in the series to damage Luffy's Straw Hat. Luffy also interfered with the schemes of Kuro, Don Krieg, and Arlong and ended up derailing their ambitions.
Grand Line Pirates
Luffy has passed several islands along the Grand Line, including Drum Island, Little Garden, Alabasta, Skypiea and Long Ring Long Land. He has met enemies even more formidable than the foes he encountered in East Blue. Starting from Whiskey Peak, Luffy and his crew became targets of Crocodile and his organization, Baroque Works. Wapol first met the Straw Hats on their way to Drum Island and antagonized them by eating a bit of their ship. When Luffy met Wapol again on Drum Island, Luffy sent Wapol flying, keeping him out of Drum Island for good. When the Straw Hats finally reached Alabasta, the crew struggled to foil Crocodile's scheme for the sake of their friend, Princess Vivi. In Long Ring Long Land, he faces Foxy the Silver Fox and his crew.
The Eleven Supernovas
His personality has left an imprint on a few of his rivals, with both Trafalgar Law and Eustass Kid being left with respect for him after he boasted he would be the one to find One Piece. They departed on good terms and all three agreed to meet up again in the New World. Luffy does despise Kid for ordering him around and says he'll crush him when they meet in the New World. Other rivals among the Eleven Supernovas are not so happy with Luffy, with Bonney claiming that she would finish them off herself if she ever met them in the New World, upset with Luffy causing trouble for her and the others by forcing an admiral to move to their location. Though she and Luffy have yet to actually meet face-to-face, Luffy's actions during the Celestial Dragon incident have unintentionally garnered him Bonney's fury, a fury that even extended to the rest of the Straw Hats (though this may simply be due to her earlier interactions with Zoro, whose ignorance she had to put up with). Upon hearing of Luffy's attack of a Celestial Dragon, Basil Hawkins was the only one whose position as to leaving or staying was unclear - all he said was that "There is no need to rush. Our destiny has already been decided."
Hody Jones and Vander Decken IX
After the Straw Hats arrive at Fishman Island, they became enemies of Hody Jones and the New Fishman Pirates for crushing Arlong's ambitions. Luffy has gained a deep hatred towards Hody's treatment towards his men and the people of Fishman Island for trying to destroy everyone. To that end, Luffy defeated him and stopped his takeover. Even after his defeat, Hody demanded a rematch with Luffy despite corroding his body beyond repair. Luffy also antagonized the captain of the Flying Pirates, Vander Decken IX, for standing between him and the object of his desires, Princess Shirahoshi.
Marshall D. Teach
When Luffy first met Marshall D. Teach in the Wild Cherry on Jaya Island, they were rivals over some petty things like favorite foods. After Luffy got mocked by Bellamy for being a dreamer, Blackbeard gave the Straw Hat captain a friendly speech telling him not to give up on his dreams, despite his later attempt to capture Luffy as a means to attain the Shichibukai position left by Crocodile. However, during the mass breakout attempt in Impel Down, when Luffy learned that the man he met on Jaya was Blackbeard, the one responsible for Ace's capture and impending execution, Luffy flew into a rage and attacked him. Though this led to them becoming enemies, Blackbeard continued to encourage Luffy to pursue his dreams.
Luffy initially thought of Big Mom as a good person for protecting Fishman Island in place of Edward Newgate. However, this soon changed when Luffy realized that she is willing to destroy a country for candy. When Fishman Island is under the threat of facing Big Mom's wrath for the lack of candy, Luffy talked with the Yonko and took the blame on himself by saying he ate all ten tons of candy. Linlin refused Luffy's offer of treasure in place of the candy and decided to target Luffy in place of Fishman Island. Luffy declared that he would defeat her in the New World and would make Fishman Island his territory.
Since Luffy agreed to collaborate with Law in defeating Kaido and decimating his forces, that would make Luffy an enemy of Kaido as well. Even though Law stated that the chances of success are slim, Luffy isn't afraid to oppose Kaido and even declared that he will defeat all of the Yonko.
Neither his mother nor his grandmother have been shown, in the Grand Line Times a "?" was left in the place of both Dragon and Garp's wives. Though Oda may not decide to ever state who the women in Luffy's family are, this leaves the spot open to suggest they may be mentioned later.