Summary:
The entire Fish-Man Island celebrates the capture and defeat of Hody and the New Fish-Man Pirates by the Straw Hat Pirates, who themselves plan to leave Fish-Man Island soon, while Jinbe reluctantly tells Luffy that he cannot join his crew. at the moment, but will be in the future when they complete their own tasks and commitments. All are soon summoned to celebrate their victory at Ryugu Palace with the banquet that was originally planned.
As the party begins to die down, Robin questions and discusses with King Neptune the disturbing and dangerous mystery surrounding his daughter Shirahoshi, Noah’s Ark, and the mysterious Joy Boy. Robin reveals the location of the ancient Skypiea weapon she read two years ago on Fish-Man Island and that Poseidon is on the island and deduces that the mermaid princess was named Poseidon during the Void Century and learns that the Shirahoshi is now the current ancient weapon, Poseidon .
The royal family decided to release the human slaves who were under Hody’s control as they were only on this island for rest and travel like other pirates. The rest of the New Fish-Man Pirates have also been released, but they cannot return to the Fish-Man District. They are ordered to live on the main island working for the king under the watch of Neptune’s army with the declaration that they will not allow the Fish-Man District to get out of control again. From this day on, the Fish-Man District will be closed and no one will be allowed to enter. Neptune then asks Fukaboshi where Luffy is and he says that Luffy escaped with the others.
The scene changes to the Straw Hats flying over the island on the Thousand Sunny, still holding the bubble balloon. Shirahoshi walks along the side of the ship and asks why they were in such a hurry. Zoro is angry at himself for fighting in such a large open area. Shirahoshi says if they stayed longer, people would lift them up as heroes and shudder at the thought. Zoro tells Shirahoshi that the heroes have to share their alcohol, which he doesn’t want to do. Nami is horrified to hear Zoro recite the same reason Luffy told Jinbe. Nami looks over her shoulder to see Luffy trying to convince Jinbe to join the crew. Jinbe replies that he can’t join but is very happy to be asked. He tells them that he has some business that he has been putting off for a long time. After taking care of it, he promises to get back to them, asking them to promise to invite him again if they still see him fit to join. Sanji tells Luffy not to corner Jinbe. Robin comments that he has taken a liking to the crew. And Franky notes that of course they would be waiting for the man who captivated Luffy as much as Jinbe. Zoro then asks if they should head to the New World now. Shirahoshi is upset at their departure and asks them to stay so she can thank them all. Sanji takes this opportunity to suggest staying at the Mermaid Cafe for the week. Usopp slaps him and says there’s only one reason Sanji would go there, but agrees with him.
Ammunition Knight calls out to them and then informs Neptune through the little Den Den Mushi that they have caught up with the Straw Hats’ ship. Through Den Den Mushi, Neptune tells Luffy that he wants to pick up where he left off with the banquet he originally promised. Luffy agrees and tells Neptune that he will also get Hatchan and Camie.
The scene briefly changes to the Fish-Man District where all the buildings are wrapped in yellow tape. He then goes to the Ryugu Palace, where Hody, his officers, and Vander Decken IX are all in a prison cell, still unconscious. At the main entrance to the island, the guards tell Surume to take Wadatsumi to the far end of the land and tell the giant fish man that they don’t have a cell to contain him and that he is being banished from the island. In Coral Hill, people are preparing food to bring to the palace feast. They carry big racks of kingfish meat, boxes of seaweed cakes and other sweets, and alcohol by the cart, enough to bathe in, as one fisherman put it.
At the palace, the straw men and their guests are carried on two large flats into the banquet hall, a completely flooded room, which makes some of the Straw men nervous. Below them, on a floor full of soldiers, the guards cheer and say that the heroes have arrived. Luffy says not to call them heroes because they eat all the meat. Shirahoshi points Luffy to the stage at the front of the room and they notice someone standing on it. The woman on stage is introduced as Maria Napole, a singer called the diva of the ocean floor and the pride of the island. Maria Napole starts to sing and her voice completely enters Nami and Usopp who feel like they might melt listening to it. Brook is excited to notice Marie Napole’s accompaniment, a jazz quintet. The music starts and then it’s Sanji’s turn to be in awe as the Mermaid Cafe dancers are introduced. More mermaids arrive, carrying trays of food, which they take from the Straw Hats and the other people present. Everyone is singing, dancing, cheering and enjoying the festivities. Pappag dances with the Medaka Mermaid Quintuplets. Luffy and Jinbe are eating and laughing with the other two mermaids. Zoro, Franky and Hatchan are roasting gourds of alcohol. Sanji turns to stone in the arms of two mermaids while another grabs Brook and starts kissing him on the cheek. Luffy is then seen having a toast with Usopp, Neptune, Shirahoshi, Camie, Jinbe, and the Minister of Right. All soldiers raise their glasses high. Robin is seen laughing and drinking with the Left minister. Brook plays guitar on stage with Maria Napole. Nami is seen celebrating her victory against Fukaboshi in a drinking contest while Ryuboshi and Manboshi dance together.
Robin is then seen standing just outside the banquet hall when Neptune, a bit tipsy from drinking, stumbles out. He asks Robin what she wanted to talk to him about. Robin apologizes and says she thought they could be alone. Believing that Neptune is after him, Robin starts telling Robin that he can never betray the love he has for his wife, even though she may be dead. Before he can continue, Robin interrupts and asks who Joy Boy is. Neptune drops the gourd in surprise. Robin goes on to tell him that she read the poneglyph in the Seawood and then asks Neptune who it was and what he was apologizing for. Neptune, who immediately sobers up, is surprised that Robin can read poneglyphs. Robin explains that she’s from Ohara and Neptune doesn’t have to tell her anything he doesn’t want to. Neptune says he will tell her what he knows knowing he can trust her.
Neptune explains that Joy Boy was a person from the surface who lived during the Void Century. His message was for a mermaid princess living on the island at the time. It’s an apology for breaking the promise he made with the island. Neptune tells her that he doesn’t know the details of the promise, only that one day someone is supposed to come and fulfill the promise Joy Boy made. He explains that it is a legend passed down in the royal family. Neptune says their promise to Joy Boy was to watch over Noah and keep him safe. Only when the promised time comes will Noah’s purpose be known. Robin tells Neptune that she heard that Noah, after the events in and above Gyoncorde Plaza, was taken by the Sea Kings to the Sea Forest. Robin asks Neptune if Joy Boy could control the Sea Kings. Neptune tells her that the ability belongs to the mermaid princess from then and now. Robin then concludes that Shirahoshi has the ability, confirming her theory. Neptune says he is right and today that ability has been fully awakened which is not a good thing. Robin agrees. She then tells Neptune about the Poneglyph she read when she was on Skypiea two years ago. It gave the location of one of the ancient weapons and said it was on Fish-Man Island. She then asks Neptune if the mermaid princess from Joy Boy’s time had a different name. Neptune begins to understand and begins to fear what he is about to listen to. Robin tells him that by having the same ability, Shirahoshi also inherited the same name as her princess. Her other name is the ancient weapon, Poseidon.