Byakuya is a priestess from the moon. She shows the mysterious power to wield Chizakura when she fights Maimai, and turns into a beautiful young woman. In the last volume she says that she was the founder of the moon kingdom and disguised herself as an old woman to hide her silver hair.
Byakuya (白夜) means "White Night" in Japanese.
Byakuya's soul symbol is unknown.