In Japanese mythology, Tsukuyomi is the Shinto moon god and brother/husband of the sun goddess Amaterasu. He is one of the three noble children' born from Izanagi, along with Amaterasu and Susanoo, after he had returned from yomi (the underworld) when he had tried to retrieve his dead wife, Izanami. The name Tsukuyomi is a combination of the word moon, along with either reading or watching. There is very little known about Tsukuyomi and some scholars believe that he and Susanoo are actually the same god.

Via Shinto Cocoro

One myth that features Tsukuyomi explains that his wife/sister Amaterasu sent him to represent her at feast put on by Ukemochi, the goddess of food. Ukemochi created the food for the feast by spitting it out, or coughing it up. Despite the food looking delicious, Tsukuyomi was disgusted by the manner in which is was produced and proceeded to kill Ukemochi. Amaterasu was so angry that she never wanted to look at Tsukuyomi again. She fled to the opposite side of the sky and stayed there forever, which created the separation of day and night. There are other accounts of the tale in which Susanoo is the one who kills Ukemochi.

Tony Perna

'Tsukuyomi' - Shoto Museum of Art, Tokyo

Artist unknown

'Plum Blossom at Night' - Ohara Koson
'Full Moon at Kankai Pavillion' - Kawase Hasai, 1950.