The movie takes place during the Pirates Festival, "made by pirates, for pirates", where pirates all over the world, including some of its most infamous ones, join in for a big treasure hunt to find a lost treasure, this time the treasure belonged to none other than Gold Roger!
Changing Tides: The Demon Heir's Freedom
After the Blackbeard Pirates broke into Impel Down and made the Level 6 prisoners fight each other to the death, Jesus Burgess realizes one more prisoner staring at them from a distance. When Marshall D. Teach noticed him, he informs Burgess that they were to leave him be. As the Blackbeard Pirates walk away, Teach is quietly shocked that the prisoner, "Demon Heir" Douglas Bullet, the fearsome pirate who worked under the Pirate King Gol D. Roger was still alive. They leave Bullet to escape Impel Down on his own.
Two years later, Bullet links up with Buena Festa, a pirate who was once thought to be dead, and Buena devises a plan to gather famous pirates from around the world to resurrect the Pirates Festival. He explains to Bullet that they will put Roger's treasure on the line to create the dawn of a new era in piracy.
The Pirates Festival Begins: Uncovering Festa's Plot
The Straw Hat Pirates arrive at Delta Island for the Pirates Festival, excited to fight for Roger's treasure. After doing some shopping and enjoying some of the events, they decide to participate in the main event. Donald Moderate and Ann who were the MC's of the event, reveal a cryptic clue for the location of the Pirate King's treasure.
Elsewhere, an injured Law was running away from Buggy and his crew who were acting as security for the Expo. Law then noticed the Thousand Sunny and used his ability to board their ship in order to escape his pursuers. Suddenly a Knock Up Stream exploded in the central lake of the island, launching an island floating in a bubble, revealing itself to be the hiding spot of the treasure. The pirates sail up the Knock Up Stream, amongst them are crews from the Worst Generation (except for the Blackbeard and the Heart Pirates), the Barto Club, Beautiful Pirates, Foxy Pirates, and the Bliking Pirates. The Straw Hats manage to overtake everyone on the Knock Up Stream by converting the Thousand Sunny into its Flying Model and using Coup de Burst, which also blasts away the Buggy and his crew who were pursuing them to capture Law.
Partway up the Knock Up Stream, Law comes out of the Sunny's lower deck, revealing that the event is not what it seems and that Buena Festa is up to something. He was able to have his crew evacuate the island, but wants to investigate the matter further. Robin, Sanji, Chopper, and Brook go with him, and they depart on the Shark Submerge III, while the rest of the crew finish the Treasure Race. Robin manages to sprout wings to let the submarine fall safely into the bay far below. Meanwhile, in Festa's underground lair, the Master of Festivities talks with Douglas Bullet, saying the time would be soon for them to put their plan into action.
The pirate crews make it up to the Treasure Island, and they soon spot a wrecked ship surrounded by heaps of treasure. An all-out brawl quickly breaks out as the pirates fight to get to the treasure, and Luffy gets into fights with Scratchmen Apoo and Urouge while Zoro clashes with Killer.
On Delta Island, an undercover Smoker leaves an undercover Tashigi behind as he goes to investigate Buena Festa. Meanwhile, Law's group sneaks into Festa's lair as well, and Robin and Brook use their abilities to spy on Festa. There, they overhear Festa making plans to have the Marines launch a Buster Call on Delta Island, leaving them aghast. As they attempt to escape, they run into Smoker, who immediately attempts to capture them. Sanji stops him from catching Robin, and she and Law run off while he battles Smoker.
Battle on Two Fronts: Douglas Bullet Arrives
Back on the Treasure Island, in the midst of the battling, Buggy manages to sneak toward the chest containing Roger's treasure and steal it. However, he is soon spotted and chased as the other pirates do whatever it takes to get the treasure.
Suddenly, a galleon is thrown at the Treasure Island which abruptly explodes, destroying both the island and the Knock Up Stream, causing everything to fall back into the central lake. While falling, Usopp finds himself next to the chest with Roger's treasure and grabs it. The pirates are left in chaos as the Devil Fruit users have to be saved from the bay by their comrades, and after the rescues are made, the pirates look in shock as they see Douglas Bullet holding a defeated Usopp. This isn't the end of their problems though, as Donald Moderate, Ann, and the spectators, notice that a Marine fleet is heading towards the island, causing virtually everyone to flee in terror.
Luffy immediately confronts Bullet as the pirate attempts to kill Usopp, and Bullet ends up throwing Usopp at Luffy as he overwhelms Luffy with sudden speed. Bullet says that he wants to challenge the Worst Generation after hearing of their exploits, and he unleashes a massive blast of Haoshoku Haki that knocks out most of the pirates. Luffy, Eustass Kid, Killer, Basil Hawkins, Scratchmen Apoo, Capone Bege, Jewelry Bonney, X Drake, and Urouge stay behind to fight Bullet, with Luffy neutralizing Bullet's Haki with his own, while the remaining pirates move to flee from the island.
Bullet begins fighting the Worst Generation and quickly overwhelms them with his sheer speed and immense strength. Apoo attacks Bullet with combat music, but the explosions do not affect him at all. Bullet easily bats away cannonballs shot by Bege and shrugs off X Drake in his allosaurus form. Bonney attempts to turn Bullet into a child, but he grabs her and slams her into the ground before she can get near him. Killer strikes Bullet with his scythes, but Bullet easily blocks them with Busoshoku Haki, and he is not overwhelmed by Hawkins' Goma no So form. Bullet goes on to resist a strike from a powered-up Urouge, easily damage Bege in his Big Father form, and redirect two large attacks from Luffy and Kid to cause them to hit each other. Afterwards, the Supernovas are all left utterly overwhelmed, with Bullet not slowing down.
However, Luffy gets up and activates Gear Fourth: Snakeman. In this form, he barrages Bullet with rapid, direction-changing punches, though Bullet returns many of the punches. Their fight ends with each fighter giving the other a powerful punch to the face and sending them flying far away. However, as Luffy lays on the ground exhausted, Bullet gets up and is not any worse for wear. Bullet mocks the Supernovas' strength, saying they have not done nearly enough to reach his level. He then decides to step it up a notch and brings out his ship, the Catapult, from underground. He uses his Gasha Gasha no Mi abilities to change the composition of the ship and the iron weapons inside of it, forming them into a gigantic robot of his control. While in the robot, Bullet states that the treasure of Roger that he currently possesses is equivalent to having the One Piece, shocking the Supernovas. With the Catapult, Bullet utterly overwhelms the Supernovas, who have no way to stop him. Bullet is able to make his already powerful root even stronger by imbuing it with his Haki, and the battle ends as all of the Supernovas lying on the ground thoroughly defeated. Bullet prepares to kill Luffy by stomping on him, but Usopp tries to stop him by shooting projectiles at the exoskeleton. They appear to have no effect until one of them sprouts into a plant that tears off one of the robot's fingers, and Bullet responds by creating a cannon which he fires on Usopp.
Meanwhile, the rest of the pirates head to the coast, only to see the Marine fleet heading toward them. Sentomaru leads a battalion of Marines and Pacifista on the coast to attack the pirates, and the Foxy Pirates plead for the Straw Hats to protect them while the Buggy Pirates look toward Buggy. Admiral Fujitora makes his way to the coast, where he clashes with Zoro. The Bliking Pirates attempt to sail out, but their bow is suddenly sliced off by Dracule Mihawk on his boat. His arrival is accompanied by the arrival of Boa Hancock and the Kuja Pirates, and the Marines uneasily think that the two Warlords of the Sea have come to provide assistance, though Hancock is only interested in finding Luffy, and Perona attacks the Marines with her Negative Hollows.
Underground, Sanji and Smoker continue fighting until Sanji asks about why the Marines agreed to work with Festa to send a Buster Call here. Smoker is surprised to hear the news and receives a call from Tashigi revealing what is going on up above, causing him to abandon the fight to take care of business. Meanwhile, Law and Robin are approached by Crocodile, who has a plan regarding Bullet that he wants to share with Law. After speaking to Crocodile, they manage to find a map to guide them off of the island. Meanwhile, Buena Festa sits back on top of a tower as he contacts the Emperors of the Underworld to show what he has in motion. He reveals that Roger's treasure is an Eternal Pose pointing to Laugh Tale, and proclaims that with Bullet's possession of the treasure and quest to defeat every powerful person in the world, he will start a new era greater than the one Roger started.
The Marine battalion makes its way to the town, where they engage in a large-scale clash with the pirates. Koby, Hina, and Helmeppo participate in the fighting on the Marines' side, but the fighting is soon interrupted as Bullet makes his way to the town in the Catapult. Sensing the new development, Fujitora decides to depart from the coast and brings down a meteorite as a parting gift. As the pirates around him wallow in terror, Zoro leaps toward the meteorite and manages to cut it in half. However, the two halves of the meteorite still threaten the pirates below, so Mihawk steps in and cuts it into tiny pieces before departing from the island.
Stopping the Stampede: A Teamup of Unprecedented Proportions
At the town, Bullet surveys the fleet surrounding him and reveals that he awakened his Devil Fruit power. He then spreads out the composition of his exoskeleton and covers the majority of the island, including the Marine's fleet and the pirates' ships' with it, ripping it all apart and assimilating it into his creation, forming an enormous colossus. The Marines and pirates are left in extreme panic, and the Marine Vice Admirals attempt to charge the colossus, but are knocked out in one punch, which is so powerful it tears apart the island itself. Bullet then raises the coast into high walls, preventing people from escaping the island. Festa proclaims that Bullet's power and their possession of the Eternal Pose to Laugh Tale have ended the era, and the new era would be defined by the people's struggle to overthrow Bullet. He tells the Underworld Emperors that Bullet would kill all of them, and Bullet sets his sights on killing the Four Emperors. Meanwhile, Kizaru contacts Sakazuki about what happened and Sakazuki orders for a Buster Call to attack Bullet and Delta Island.
Meanwhile, at Marine Headquarters, Brannew briefs the Marines about Bullet's past. In his youth, Bullet was a soldier in the land of Galzburg, and ultimately massacred the people there. He proceeded to become a pirate and challenge Roger, who gave him a taste of defeat. Bullet joined forces with Roger and attempted to kill him many more times, but never succeeded in beating Roger before the Pirate King was executed. After Roger died, Bullet went berserk and headed on a rampage until he was finally stopped by a Buster Call led by Garp and Sengoku. In the present, Garp heads outside and talks with Sengoku, reflecting that Bullet lost his way after losing Roger. The two Marine heroes are very apprehensive about the threat the pirate currently possesses.
Meanwhile, a heavily injured Usopp carries an unconscious Luffy to find help. They stop in the path of a falling building, and Usopp stops a large burning pole from falling on Luffy, but collapses as the rest of the building start to fall on them. However, Brook then arrives and stops the collapse by freezing the building, and Chopper arrives to treat their injuries. Usopp tells him to focus on treating Luffy, as he had lost a lot of blood. After receiving treatment, Luffy wakes up soon afterward. Usopp tearfully apologizes to him for not being strong enough to protect him, but Luffy has no issue with it and wants to go after Bullet right now. Despite Chopper's protests, Luffy activates Gear Fourth and flies toward Bullet.
The Buster Call comes within view of Delta Island, and the Marines attempt to escape on a ship before the Buster Call starts attacking the island in mere minutes. Smoker elects to stay behind on the island, and Tashigi, Koby, and Helmeppo want to go with him, but Hina binds them with her Devil Fruit power and drags them away. Meanwhile, as Rob Lucci looks on at Bullet's colossus, Hancock searches for Luffy. She finds a red object surrounded in debris that she mistakes for Luffy's vest and pulls on it, only to realize that it is Buggy's nose. Smoker attempts to attack Bullet, but is then stopped by Sabo, who fights him to a draw. They then encounter Hancock and Buggy, former who is looking for Luffy. Law then approaches the group as they see Luffy flying toward Bullet's colossus, who sees him and immediately overwhelms him. Luffy is sent toward Law's group's location, and Law tells the group about his plan to take down Bullet. He reveals that Bullet's creations could be weakened if they were broken apart, but Bullet's powerful Haki made them difficult to damage. Law says that he can cut a gap in Bullet's Haki with his abilities, but before he can go over the rest of the plan, Luffy flies off to attack Bullet again.
Bullet immediately overwhelms Luffy again and sends him flying across the island, and in retaliation, Hancock raced up the colossus and planted a powerful kick to its torso, causing Bullet to temporarily reassemble the colossus. Crocodile, who was waiting for this opportunity, created a sandstorm toward the colossus, preventing it from fully reforming. Law then activates a ROOM and uses Shambles to replace parts in the colossus' right shoulder with rubble, leaving it weak enough to attack. Sabo and Smoker attack in unison, and succeed in blowing the colossus' right arm off. Bullet attempts to extend his shoulder to reattach the falling arm, but Lucci, who was observing from a distance, destroys it with a series of Rankyaku kicks.
Bullet is confident that he can overpower his enemies even with just one arm and gears up to attack them. Though the allies are briefly discouraged, after noticing Luffy preparing a powerful attack, Law's group performs one more combined attack which blows away a portion of the torso. This allows Luffy, who inflated his fist to a massive degree and flew toward Bullet to attack him with it, resulting in their giant fists clashing. After a long and powerful clash, Luffy's Gomu Gomu no King King King Kong Gun manages to overpower the colossus, and Bullet is forced out of it, though the Catapult still remains. Fortunately, the force of Luffy's punch causes the seeds Usopp had fired earlier to sprout into Hebi Hanabi, thick powerful vines that wrapped around and cracked open the Catapult, severely injuring Bullet in the process.
As Bullet is forced out of his ship, both Crocodile and Rob Lucci attempt to take the Eternal Pose, but are stopped by Zoro and Sanji respectively. Bullet takes on Luffy in a brutal fistfight, and both fighters trade punches with impunity. Bullet uses his Haki to keep up with Luffy's ferocity, eventually covering his entire body in it. Luffy charges toward Bullet and inflates both of his fists, barraging him with Gomu Gomu no King Kong Gatling. This barrage eventually overwhelms Bullet and sends him crashing into the ground, defeated.
Following Bullet's defeat, Festa mourns over the failure of his plan. Sabo then comes to confront him, and Festa attempts to quickly shoot Sabo with a pistol, but Sabo strikes first as he uses Hiken to defeat the festivities master. Festa realizes Luffy's ability to turn those around him into allies, saying he should have teamed up with him instead. Sabo replies that Luffy would never team up with someone like Festa.
In the aftermath of the fight, Luffy stands with the Eternal Pose in his possession, and Crocodile and Lucci once again try to get it. However, Luffy destroys it by crushing it in his hand, claiming he does not need it to reach Laugh Tale. He and his crewmates make it back to the Sunny, but their escape route is blocked by the Buster Call fleet. However, the other members of the Worst Generation start sailing out as well, posing a greater challenge to the Buster Call. Sabo returns to the Revolutionaries' ship, which has rescued Ann, and he asks Ann if she can form a certain illusion for him. As the pirates sail out, Kizaru attempts to attack them with several light beams, but his attack is blocked by Sabo creating a wall of fire. The fire wall also gives the pirates a safe passage through the fleet, and as Luffy looks back, he sees Sabo along with an illusion of Ace made by Ann. Additionally, Smoker contacts Kizaru, saying to stop the Buster Call as there is no longer a need for it.
In a post-credits scene, it is revealed that Roger had disapproved of his subordinate making an Eternal Pose to Laugh Tale and threw it into the ocean, saying that the One Piece could not be obtained by someone who used it. In the present, the Straw Hats find out what the treasure is and that Luffy destroyed it. Most of them except for Usopp are shocked at what Luffy did, but Luffy says that he did not want to miss out on any adventures.
The Straw Hats are attacked by the bounty hunting Cidre Guild as their leader, Cidre, prepares to go to the Pirates Festival to kill Douglas Bullet. After escaping the Cidre Guild, Luffy disembarks on an island to replenish the Thousand Sunny's cola supply. There, he reunites with Hancock, and Cidre and the Cidre Guild attempt to kill the two of them. Luffy and Hancock manage to quickly defeat them, and Luffy obtains Cidre's Pirates Festival invitation, leading the Straw Hats to head to the event.
Teach, Perona, Law, Kid, Hawkins, Apoo, and Hancock were shown as kids in the end credits of One Piece Film: Z.
This film is the first since Strong World to have its soundtrack used in the anime series.
In the post-credits scene, Roger says that his crew came too early and that the next person to find One Piece would be his son. He would later say this in the manga five months after this film's release.
In the scene where a group of designated Marine Vice Admirals attack Douglas Bullet, CaptainShu is seen attacking with them. It is unknown if this means he had been promoted from Captain to Vice Admiral or if it is a non-canon story error.
Kid, Bonney and Hancock are the only secondary characters showing new abilities or techniques never seen before in the series (Kid is shown able to use Busoshoku Haki; Bonney displays a distraction tactic to throw eggs that can develop into birds quickly with her powers; Hancock shows her Perfume Femur Magna).
Excluding Luffy, Zoro and Law, the designs of the Supernovas are the same as the anime but with different colors.
For unknown reasons while being in his second outfit, Buggy's hair color is changed from blue to light yellow.
In the post-credits ending where the crew found out that Luffy destroyed the Eternal Pose, Zoro is seen wearing his pre-timeskip outfit.