The Japanese moon god killed a food goddess at a banquet for serving food she had produced from her own body, and his sister the Sun has refused to share a sky with him since.

Amaterasu called it unforgivable and moved away, which is why day and night are separate. Tsukuyomi is one of the three noble children born when Izanagi washed his face — Sun from the left eye, Moon from the right — and he has almost no other stories, which makes him one of the least developed major moon gods anywhere.