Urashima Taro was a kind-hearted fisherman who saved a sea turtle from some children beating it. The sea turtle was actually a princess who thanked him by inviting him to her Dragon Palace under the sea. They fell in love and married. Eventually, Urashima grew homesick for his parents so the princess let him return home but warned him not to open a box she gave him. When he found that centuries had passed and his parents were gone, he opened the box and died, unable to return to the underwater palace.