Irina, the third daughter of the three Nemoto sisters, is a plain, college science student who wears a white coat and glasses at school. It seems that things are going well with her boyfriend Soga. One day, while Irina is studying ancient Japanese history, she discovers a system in which women share a man sexually.
Akika Kitagawa
as Irina Nemoto
Anna Tomo
as Masami Nemoto
風間恭子
as Oriha Nemoto
吉岡睦雄
as Sokuten Soga
なかみつせいじ
as Toshihiko Mitsukawa
平川直大
as Ginichi Kuwai
