Tsumugi Yuuki can be described as shy and determined. She is an electric pianist in the same band as Karasuma. She is often seen with Mai or with her band. Although she is shy, she is by no means a pushover. During the survival game, she showed how she was a force to be reckoned with. She is also a member of the Astronomy Club. In the Manga, Yuuki makes her first appearance in chapter 22 “Duel," cheering on the Pool Battle.