Having subdued his brother, Yamasachi-hiko receive joyful news: Toyotama tells him that their child will be born soon and that Yamasachi-hiko should build a hut for her to give birth in. She says that this structure should be on land, because a descendant of the gods of heaven must not be born in the sea. Yamasachi-hiko starts building a hut for his wife, but she goes into labor before in the roof, made of cormorant feathers, can be completed. Toyotama enters the hut and implores Yamasachi-hiko not to look at her before the baby is born. Yamasachi-hiko, however, cannot resist the temptation, and sees Toyotama, the daughter of the sea, transformed into a giant shark. Her true from revealed, Toyotama returns to the sea in anguish, leaving her newborn baby behind. The child receives the unfortunate name of Ugayafukiaezu, or “the one for whom the cormorant-feather roof was not finished in time.” He is brought up by Toyotama’s sister Tamayori, whom he marries after reaching adulthood.

Ugayafukiaezu is enshrined as a Shinto deity at Udo Shrine in the city of Nichinan. According to local beliefs, the coastal cave that houses Udo Shrine is his birthplace.