Urashima Taro

In the Japanese folktale Urashima Taro, a fisherman saves a turtle who is being tortured by two children and returns it to the sea. The next day he is approached by a huge turtle who informs him that the turtle he saved was in fact the daughter of the dragon king who lives beneath the sea, and who now wishes to meet with him. Urashima then rides upon the turtles back, and with the help of some magical gills, is taken deep beneath the water to arrive at the magical palace of the Dragon King at the bottom of the sea. Urashima Taro is entertained by the King and his daughter Princess Otohime as a reward for his kindness.

'Urashima Taro Returning Home from the Palace of the Dragon King' - Tsukioka Yoshitoshi

He enjoys what he believes to be several days at the underwater palace but then realises he wishes to return to his village to see his aging mother. The princess is sad that he wishes to leave, but gives him a magical box which she says will protect him from any danger. She warns him though that he is not to open the box for any reason. Urashima jumps on the back of the turtle and waves farewell before he is returned to the shore.

'Urashima and Dragon Palace' - Ogata Gekko, 1893
When he arrives he discovers that everything has changed and he can't find anyone he knows. He soon learns that 300 years have passed since he left to visit the Dragon King. Filled with grief, he absent-mindedly opens the box given to him by the princess and suddenly turns into an old man. He hears a mysterious voice floating over the sea saying 'I told you not to open the box, it contained your old age.' Many folktales from both Japan and Korea refer to the legendary Dragon King and his palace under the sea.
'At the Palace of the Dragon King' - Utagawa Kuniyoshi, 1853

'Urashima Taro and Princes Horai' - Matsuki Heikichi, 1899.

'Urashima' - Kawanabe Gyosai, ca. 1880

'Urashima Taro and the Dragon Princess' - Katsukawa Shunko

'Coming Back on a Magic Turtle' - Tsukioka Yoshitoshi, 1882.

From Jinjo shogaku kokugo tokuhon