One of Keiichi's friend, Shion's twin sister and the leader of the after-school club. Her social skills are on par with Keiichi, whom she highly respects as a friend and rival. She acts like a tomboy, and calls herself oji-san (meaning old man), but has a hidden girlish side. She is next in line to be the head of the Sonozaki household, one of the Three Families holding tremendous influences. She is often seen with a holstered airsoft gun, even though she does not use.