Mizumoto Marina

Favorite food: Konjac chocolate, shiitake jelly, supplement foods
Hobbies: Ordering diet-related and health equipment, window shopping, reading fashion magazines
Troubles: She's still a virgin.

Yuuya's cousin who has been together with him ever since they were young and acts like an older sister to him. She has an older sister who happens to be a teacher as well, and Marina teaches both World History and Ethics. Despite her appearance she is the adviser for the wrestling club, and enjoys muscle training at the school's gym as well.