Shuu Tsukiyama's mother was the mistress of the illustrious Tsukiyama family, and wife of Mirumo Tsukiyama. Little is known about her, other than the fact that she passed away while her son was quite young.
Little is known about her appearance, though it is stated that her son greatly resembles her. As such, it's likely that she was a very beautiful and elegant woman.
Her husband recalls their marriage as passionate, and hopes that their son will one day experience a similar romance. As such, it's likely that the couple were very happily married until her death. He continues to set out a placement for her at the table, even after so much time has passed since her death.