"Revealed Secret - The Truth of Ancient Weapons" is the 569th episode of the One Piece anime.
As the whole Fish-Man Island celebrates the capture and defeat of Hody and the New Fish-Man Pirates by the Straw Hat Pirates, who make their own plans to leave Fish-Man Island soon while Jinbe reluctantly tells Luffy that he cannot join his crew at the moment but he will in the future when he is finished his own tasks and obligations. They are all soon called to celebrate their victory at the Ryugu Palace with the banquet that was originally planned.
As the party begins to wind down, Robin asks and discusses a troubling and dangerous secret with King Neptune surrounding his daughter, Shirahoshi, the ship Noah, and the mysterious Joy Boy. Robin reveals the location of the ancient weapon from Skypiea she read two years ago being on Fish-Man Island and that Poseidon is on the island and deduces that the Mermaid Princess during the Void Century name was Poseidon and discovers that Shirahoshi is the now current ancient weapon, Poseidon.
The royal family have made a decision to release the human slaves that were under Hody's control as they were only on this island for resting and traveling like other pirates. The rest of the New Fish-Man Pirates have also been released however they cannot go back to the Fish-Man District. They are ordered to live on the main island working for the king, under the supervision of the Neptune army stating they will not let the Fish-Man District get out of control again. From this day forward, the Fish-Man District will be sealed off and nobody will be allowed to enter. Neptune then asks Fukaboshi where Luffy is and he says Luffy ran away with the others.
The scene changes to the Straw Hats, who are flying above the island on the Thousand Sunny, still toting its bubble balloon. Shirahoshi is following along side the ship, and asks why they left in such a hurry. Zoro is mad at himself for fighting in that big of an open area. He tells Shirahoshi if they had stayed any longer, the people would have lifted them up like heroes, shivering at the thought. Zoro tells Shirahoshi that heroes have to share their alcohol, something which he does not want to do. Nami is appalled to hear Zoro reciting the same reason Luffy told Jinbe. Looking over her shoulder, Nami sees Luffy trying to convince Jinbe to join the crew. Jinbe replies that he cannot 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 he has taken care of it, he promises he will come back to them and asked them to promise to invite him again, should they still see him fit to join. Sanji tells Luffy not to back Jinbe into a corner. Robin remarks that he has taken a liking to the crew. And Franky remarks that of course they would wait for a man who captivated Luffy as much as Jinbe did. Zoro then asks if they should head to the New World now. Shirahoshi is upset by their departure and asks them to stay so she can thank them all. Sanji uses this opportunity to propose staying at the Mermaid Cafe for a whole week. Usopp slaps him, saying there is only one reason Sanji would go there, but he does agree with him.
An Ammo Knight calls out to them, and then informs Neptune via baby Den Den Mushi that they caught up to the Straw Hats' ship. Through the Den Den Mushi, Neptune tells Luffy he wants to pick up where he left off with the banquet he initially promised. Luffy agrees, and tells Neptune he will get Hatchan and Camie as well.
The scene changes briefly to the Fish-Man District, where all the buildings have been wrapped in yellow tape. It then goes to 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, guards are telling Surume to carry Wadatsumi to the far ends of the earth, telling the giant fish-man that they do not have a cell that can hold him, and that he is banished from the island. In Coral Hill, people are preparing food to bring to the palace banquet. They are carrying large racks of Sea King meat, boxes of seaweed cakes and other sweets, and alcohol by the cartload, enough to bathe in, as one fish-man put it.
At the palace, the Straw Hats and their guests are being carried on two large flounders to the banquet hall, a completely inundated room, which makes some of the Straw Hats nervous. Below them on the floor packed with soldiers, guards cheer and say the heroes have arrived. Luffy tells not to call them heroes as he is going to eat all the meat. Shirahoshi points out a stage in the front of the room to Luffy, 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 begins to sing, and her voice completely entrances Nami and Usopp, who feel as if they could melt from hearing it. Brook gets excited, as he notices Maria Napole's accompaniment, a jazz quintet. The music starts up, and then it is Sanji's turn to be in awe, as the Mermaid Cafe dancers are introduced. More mermaids come in carrying trays of food that they take to the Straw Hats and the rest of the people in attendance. Everyone is singing, dancing, cheering, and enjoying the festivities. Pappag is dancing with the Medaka Mermaid Quintuplets. Luffy and Jinbe are eating and laughing with two other mermaids. Zoro, Franky, and Hatchan toast gourds of alcohol. Sanji turns to stone in the arms of two mermaids, while another one 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 the Right. All the soldiers raise their glasses high. Robin is seen laughing and drinking with the Minister of the Left. Brook is playing his 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, saying she thought they would be able to be alone. Neptune, thinking she was coming on to him, starts telling Robin he could never betray the love he has for his wife, dead though she may be. Before he can go on, Robin cuts him off, asking who Joy Boy is. Neptune drops his gourd in surprise. Robin goes on to tell him that she read the poneglyph in the Sea Forest, and then asks Neptune who he was and what he was apologizing for. Neptune, instantly sobering up, is surprised Robin can read poneglyphs. Robin explains she is from Ohara and Neptune does not have to tell her anything he does not want to. Neptune says he will tell her what he knows stating he knows 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 the Mermaid Princess living on the island at that time. It is an apology for breaking his side of a promise he made with the island. Neptune tells her he does not know the details of the promise, only that some day someone is supposed to come and carry out the promise made by Joy Boy. He explains it is a legend passed down in the royal family. Neptune says that their promise to Joy Boy was to watch Noah and keep it 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 carried to the Sea Forest by Sea Kings. Robin asks Neptune if Joy Boy could control Sea Kings. Neptune tells her that ability belongs to the Mermaid Princess from then and now. Robin then concludes that Shirahoshi has the ability, confirming her theory. Neptune says she is right, and today that ability was fully awakened, which is not a good thing. Robin agrees. She then tells Neptune about the Poneglyph she read while in Skypiea two years ago. It gave the location of one of the ancient weapons, and said it was located on Fish-Man Island. She then asks Neptune if the Mermaid Princess from Joy Boy's time went by another name. Neptune starts to understand and begins to become fearful of what he's about to listen to. Robin tells him that Shirahoshi, by having the same ability, also inherited the same name as that princess. Her other name is the ancient weapon, Poseidon.
Characters in Order of Appearance
- When the soldiers call the Straw Hat Pirates heroes prior to the banquet, the manga only shows Luffy saying that he wants all the meat. The anime adds Zoro saying that he wants all the sake, mirroring Luffy's comment about not wanting to become a hero and have to share all the meat by saying he doesn't want to share the booze.
- The anime adds a scene in which Neptune was about to give a toast until Luffy interrupts him.
- The Medaka Mermaid Quintuplets have more appearances in the banquet in the anime than in the manga.
- The anime adds a scene in which Ishilly greets Camie and Camie says that she is glad that Ishilly is alright.
- The preview for the next episode is shortened from its usual length.