I first heard about tamate box, Otohime princess and the underwater palace in One piece but episode 9 of Kaichou wa Maid Sama also contains very similar references such as the contents of the tamate box make you old, Otohime princess etc. So I want to know if there exists a local tale or is it just KMS making a reference to One Piece.
This is the story of Urashima Taro. It's a famous old Japanese folktale from the Nara period about a man who saves the Emperor of the Sea's daughter, Otohime. He is invited to live in the underwater palace with them. He stays for three days but wants to go visit his mother. He is given a box by the princess before he leaves, and when he returns to the surface he finds that it's 300 years later and everyone he knew is dead. Distraught, he absently opens the box and ages all 300 years at once, because the box contained his old age.