"When he found a tortoise on his line, the fisher - boy named Urashima unhooked it and threw it back into the sea. Thereafter, the tortoise, disguised as the daughter of the Sea - God, guided him to the Dragon Palace, where the two married and lived happily together. One morning three years later, Urashima decided to leave the palace and pay a short visit to his family. She handed him a box, warning him not to open it under any circumstances. When he returned to his own country, Urashima discovered that 400 years had passed in the meantime. He longed to go back to the Dragon Palace, but did not know the way, and finally opened the box. Out came a cloud of smoke that instantly transformed him into an old man who died on the spot." (Kyoto University of Foreign Studies,
https://www.kufs.ac.jp/toshokan/chirimenbon/b_08.html)
