Around 800 years ago, the residents of Fishman Island made a promise to a great man named Joy Boy. Joy Boy attempted to raise Noah with Poseidon's aid, but he broke his promise to Fishman Island. However, Fishman Island promised that they would keep Noah safe until a certain day came. On the poneglyph is a letter of apology from Joy Boy to Poseidon, apologizing for breaking his end of the bargain.
Fishman Island's half of the promise was almost broken during the events of the Fishman Island arc, when Luffy was asked to protect the island no matter what the cost, even if Noah had to be destroyed in the process.
- ↑ One Piece Manga and Anime — Vol. 64 Chapter 628 and Episode 548, Nico Robin reads about Joy Boy on the Ryugu Poneglyph.
- ↑ One Piece Manga and Anime — Vol. 66 Chapter 649 and Episode 569, Neptune explains to Robin who Joy Boy was.