Meet Mutsuki, a highly skilled athlete known for her exceptional abilities. Her reputation often precedes her, and she has been invited to participate in several club activities as an honorary member at school. Despite not being an official member, Mutsuki enjoys helping out where she is needed and takes part in numerous sports-club related activities, in addition to her work with the student council. She has a tomboyish personality, often hitting Mei on the back very hard and sporting a short haircut for a girl. Her mannerisms are not typically feminine, and her voice is deeper than the typical female voice for her age.
Mutsuki has known Mei Etoh since elementary school and tries to get her to participate with the other main characters as a group rather than distance herself more from them. Mutsuki was the first person Mika became friends with upon entering high school, despite their little in common. Eventually, she is inducted into the student council as the assistant.