Kyonyuu Try! Tanki Shuuchuu Chichi Momi Lesson(2014)

Based on the adult game by Marine.

Mio has been telling her students at school that her breasts are so large because her step-brother, Keisuke, rubs them daily! Students Ayano and Rin visit Keisuke, eager to take advantage of this treatment for the sake of their own busts.