Yuya has liked Kokoro since elementary school. They met by chance recently, and when he decided to confess his feelings, they started going out. In fact, Yuya's father is a teacher and was the homeroom teacher for the two of them. Yuya brings Kokoro home and introduces her to his father as his lover. However, he doesn't realize that his father's obscene gaze is fixed on Kokoro's large, growing breasts. His father calls Yuya to ask for advice about Yuya, and Kokoro, who innocently believes her teacher and listens to him, gives him an aphrodisiac and forcefully pushes him down.