Otohime (乙姫, translated as "Princess Oto"), is also known as Toyotama-hime, a sea goddess in Japanese mythology. She appears in the episode of the "Luck of the Sea and the Luck of the Mountain" in the Kojiki as well as Nihon Shoki. She is the daughter of the Sea-Deity, Watatsumi. The palace where they reside is said to be as if made from fish-scales, and supposedly lies undersea.
She makes a fateful meeting with the hunter prince, named Luck of the Mountain (Yamasachi), also known as Fire-Subside (Hoori). The prince came in search of the fishing hook he lost at sea, borrowed from his elder brother Luck of the Sea (Umisachi).
When the princess came to draw water from the well, the prince was already waiting, having climbed a katsura tree (or cassia tree) that towered above the well. The prince asked for a drink of water, and made a gesture of spitting jewels into the vessel; the princess was captivated by his beauty. Her Sea-Deity father recognized him as the descendant of the heavenly gods, and arranged a banquet. Toyotama married the prince, and they lived together in the place for three years.
At the end of three years, Toyotama's husband let out a sigh, and revealed his unfinished quest for the lost fish hook, which needed to be returned to his brother. After the hook was found caught in the sea bream's (tai fish's) throat, Toyotama's husband was set upon a one-fathom long crocodile to return home, an with the advice from the Sea-God, subjugated his elder brother.
Toyotama, who had accompanied her husband to the land above sea, announced her pregnancy. The prince built for her a child-delivery hut ("parturition house") thatched with cormorant feathers, which was not completely thatched when she went into labour. Toyotama requested her husband not watch while she gave birth to their child. Toyotama then gave birth to a son, who was named Ugayafukiaezu ("Cormarant-Thatch-Meeting-Incompletely") or "Heavenly Male Brave of the Shore". Unfortunately, Hoori's curiosity got the better of him and he attempted to spy on his wife. To his surprise, however, rather than seeing his wife as he knew her, he witnessed an enormous wani (crocodile) cradling his child (one of Nihongi's version claim she was a dragon, Tatsu). This creature was none other than his beloved Toyotama who had shape-shifted to give birth. After catching her husband spying on her, she was utterly ashamed that he broke his promise. Unable to forgive Fire-Subside, she abandoned both him and their child by returning to the sea.
Otohime also appears in in the tale of Urashima Tarō. In the tale a young fisherman named Urashima Tarō is fishing when he notices a group of children torturing a small turtle. Tarō saves it and lets it to go back to the sea. The next day, a huge turtle approaches him and tells him that the small turtle he had saved is the daughter of the Emperor of the Sea, Ryūjin, who wants to see him to thank him. The turtle magically gives Tarō gills and brings him to the bottom of the sea, to the Palace of the Dragon God (Ryūgū-jō). There he meets the Emperor and the small turtle, who was now a lovely princess, Otohime.