浦島太郎
The protagonist of an old Japanese folktale. He stops a small turtle from being bullied, and in thanks he is brought down to the underwater palace of Ryugu-jo. He stays underwater for only three days, but when he comes back to the surface, he finds that 300 years had passed since he first went underwater. 

Tag should be used when the story is being referenced in any way or if someone is cosplaying as the titular character.
urashima tarou