Which deity is the Japanese moon god?

The Japanese moon god is Tsukuyomi.

Tsukuyomi-no-Mikoto, also called Tsukiyomi, is the moon kami of Japanese mythology and Shinto. In the Kojiki, he is born from Izanagi’s right eye during the creator god’s purification after escaping the underworld. He belongs to the important trio of siblings that includes Amaterasu, the sun goddess, and Susanoo, the storm deity.

One famous myth explains the separation of day and night. Tsukuyomi kills the food goddess Ukemochi after being disgusted by the way she produces a meal. Amaterasu is angered by the killing and refuses to meet him again, leaving the sun and moon apart in the sky.

The ancient sources do not present every detail consistently. The Nihon Shoki gives alternate accounts of Tsukuyomi’s birth and assigns him somewhat different realms. His name is often interpreted as relating to “reading” or “counting” the moon, connecting him with timekeeping and lunar calendars. He is sometimes confused with Susanoo, but Susanoo is the storm-and-sea deity.