Neptune

King Neptune (ネプチューン王) is a coelacanth merman and the king of the Ryugu Kingdom on Fishman Island. He is the father of Fukaboshi, Ryuboshi, Manboshi, and Shirahoshi.

Appearance
Neptune is a giant (shown when he clash with zoro, who is average size human), muscular, and hairy coelacanth merman. He has long curly hair and a curly beard and a darkened nose. As king, he wears a crown that resembles a tulip and carries a trident. He has matching tattoos on both arms

Personality
Neptune seems to be very blunt, as he simply invited the "Straw Hat humans" to the Ryugu Palace, instead of being more cordial. He also tends to shout his words out for no reason, including a habit of shouting his own name at random times, being followed by his whale shouting "Hoe". He appears to be easy-going, absent minded, and carefree as he was scolded by his ministers for leaving the castle on a whim on more than one occasion. However, he can be serious when the situation demands it, as he intends to capture the Straw Hat Pirates when they were wrongly accused of kidnapping mermaids, though Neptune did not think it was fair to arrest them based on a prediction made by Madame Shirley, and merely wanted to capture the crew rather than arrest them for a precaution. He doths on his only daughter Shirahoshi, and worries about her immensely. He provided several extreme but necessary security measures to protect her from Decken, and attempts to rush to her aid when he thinks that his daughter is in danger. Neptune apparently acknowledges the value of sacrifice, and opted that he'd rather risk his daughter's safety at the hands of strangers than in Decken's captivity. He gets quite upset when he hears that she is upset or in danger.

Like many other characters in the series, he appears to have a unique laugh: Hoh hoh hoh hoh.

Family and Kingdom
Neptune appears to be very protective of his family, as he had his sons form an army solely to track down Vander Decken IX so that the pirate would stop harassing his daughter. He also has a beloved whale named Hoe. The Ministers of the Left and Right tend to yell at Neptune for his lack of responsibility as the king of Ryugu, and he doesn't seem to have any resentment to that.

When he was tied up after his failed attempt to capture the Straw Hats, Neptune begged the pirates to ensure Shirahoshi's safety when he suspected that she might be in danger, showing great concern for his daughter, and warned the crew that if anything happened to Shirahoshi, he would hunt them down to the ends of the earth.

Enemies
Since Vander Decken IX kept annoying Shirahoshi with threatening letters of marriage proposals, he has earned Neptune's wrath, leading him to form an army against the pirate.

Abilities and Powers
As the king, he has royal authority over the entire Ryugu Kingdom. His presence outside the palace is enough to cause a commotion with the inhabitants referring him as "You-Know-Who".

While he is the king of Fishman Island, he has had to rely on the protection of two of the Yonkou: Whitebeard until his death and then Charlotte Linlin (Big Mam) afterwards. He didn't have to pay collateral to Whitebeard, but he does have to pay a monthly fee of sweet candy to Big Mam.

He is known to be extremely powerful in combat, but his strength seems to have weakened due to having sprained his back and old age, but he is still strong enough for the Straw Hat Pirates to tied him up with chains as opposed to the ropes used on the guards.

Weapons
He carries around a gigantic trident fitting his size, and is presumably proficient in using it, as Brook and many Fishmen acknowledged his strength. Zoro, however, seemingly stopped one of his attacks with ease, and soon after managed to subdue Neptune and lock him in chains without recieving any visible injuries.

Past
He was so angered by Vander Decken IX pestering his daughter through letters, packages, and ultimately marriage proposals, that he had his three sons form an army called the Neptune Army to capture him.

Fishman Island Arc
When Megalo tells him about being freed by the Straw Hat Pirates, he looks forward to meeting them. When he learns that Straw Hat Luffy is in Pappug's mansion, he personally travels there to meet him. After making contact with Luffy, King Neptune invites him and his crew to his palace.

The Straw Hats, Keimi, and Pappug rides on Megalo while Neptune rides on Hoe as he calls to them not to fall off. Neptune explains that Megalo is his daughter's beloved pet. She could not stop crying over how Megalo had not come home that Neptune didn't know what to do with her. He thinks about how dangerous fighting the Kraken must have been and thanks them for their great work. Luffy tells him that it was just a coincidence but he was glad to help. Neptune tells them that he had sent his sons out to get them, but when they didn't come back, he went out himself. He says that he was excited for the banquet's menu and wanted to start as soon as possible. He then remembers that one of the Straw Hats was already at the palace. He had already started drinking and wouldn't listen when Neptune suggested it would be more fun for everyone to drink together. King Neptune says that he thought his name was Zori, and gets corrected with the right name. Neptune goes on to tell them that his soldiers will find all of the other Straw Hats and bring them to the castle. Nami then asks Neptune a question about why Fishman Island is so bright despite being 10,000 meters below the surface. Neptune tells her that Fishman Island came to be when fishmen began living on the sea floor where there was light. He explains that the roots from a tree called Sunlight Tree Eve reach down to the sea floor and transfer light to Fishman Island.

They approach the entrance of the palace. Neptune rings a doorbell, saying it is him, and a stammering voice says that they will open the gate at once. Once they are in the corridor beyond the gate, Neptune said "let's go", in excitement, shouting his own name as a battle cry. Luffy says that it looked like a cool palace with a lot of stuff. Neptune answers him bluntly saying of course it would as it is his castle. He then tells everyone to enjoy themselves. Once inside the castle, two men instantly start berating Neptune for going out on his own. He tells them he will be sure to be more careful in the future. Everyone but Luffy watch this scene, realizing the king is getting yelled at and told off like a child. Neptune tells the men that he brought the people who saved Megalo from the Kraken. He also asks where his daughter, Princess Shirahoshi, is. The men tell him that "it" happened again just a moment ago. Neptune gets angry, telling the men they didn't set her up with the proper guarding to keep her from getting upset. One of the men retorts that the king disappearing during such a critical time would get the whole castle upset. He then lowers his head, apologizing and promising to take better care next time. The Straw Hats realize he is getting yelled at again. The two men who were berating the king are the Minister of the Right, a seahorse fishman, and the Minister of the Left, a catfish fishman. The Minister of the Right apologizes for berating the king in front of his guests, but they have something important to discuss with him. The Minister of the Left tells them they received a message from Fukaboshi.

After receiving word of the mysterious disappearances of the mermaids from Mermaid Cove and of Madame Shirley's ominous prediction, the palace guards and personnel took action against the Straw Hats. After some of the guards are overwhelmed by Nami, Usopp, and Brook, The Minister of the Left begs Neptune to use his power against the pirates. Neptune doesn't wish to go against them just because of a prediction. He attempts to subdue the pirates, but Zoro intercepts him.

He is next seen chained up along with his ministers and the castle guards. He comments on how he has not been able to fight all that well after straining his back. He admits that he has gotten old and apologizes for being unprepared. Neptune's sons return, but they are stuck outside since the only way in the caste is the palace entrance. Zoro then speaks with Fukaboshi through Den Den Mushi while making some demands. Neptune informs Fukaboshi that he is speaking to the pirate who is now worth 160 million. Neptune is then surprised to hear a sound coming from Shirahoshi's tower. He realizes his daughter is in danger and asks if there are guards posted by her room. He is then told that they are all tied up with him. He then orders the Straw Hat Pirates to go and make sure Shirahoshi is safe. When the guards protest, Neptune tells them that dire situations call for sacrifice. He then angrily tells the Straw Hats to go to the northeast part of the palace where the tower is located. When Zoro asks why they should take orders from a hostage, Neptune becomes even more angry, telling them that if anything happens to his daughter while he is incapacitated, he would chase the pirates to the ends of the ocean.

Major Battle

 * Neptune vs. Roronoa Zoro

Trivia

 * His name comes from Neptune, the Roman god of the sea.
 * His appearance is similar to that of Triton from Disney's "The Little Mermaid".
 * He is a coelacanth merman, the significance of this being that the Indonesian species is referred to locally as "raja laut", meaning "King of the Sea".
 * His thick beard, friendliness, and "ho-ho-ho" laugh are hallmark features of Santa Claus.