A teacher must protect their students. But in Professor Endo's classroom, there is a student with huge breasts. She is... the introverted K-cup "Koyomi Minase." She prefers to keep to herself, but she is always subjected to inappropriate comments from guys all across the school, regardless of whether they are students or instructors. Minase has no friends because of her huge breasts and constant teasing, so Endo, her homeroom teacher, does his best to protect her. As one of the only people who treat her with kindness, Minase gradually develops feelings for Endo... And so, Minase decides to seduce the kind teacher with the asset valued by all guys... her huge breasts!