Tsukuyomi (Japanese: 月読), or Tsukuyomi-no-mikoto (Japanese: 月読尊), is the god of the moon in Japanese mythology. He is the brother of Amaterasu, the goddess of the sun, and of Susanoo, the god of the sea and storms.
He killed Toyoukebime the goddess of food. His sister Amaterasu was upset at this and said she would stay away from him forever. This is why the sun is up during the day and the moon is up during night.
Mythic Texts and Folktales: