Kotaro, whose nipples are sensitive, works hard at muscle training to fix his weakness, but even though his body has become stronger, his nipples remain as sensitive as ever. One day, his mother's friend, Nozomi, comes to the house... Nozomi, who is frustrated by a lack of sex with her husband, changes completely as soon as she finds out about Kotaro's erogenous zones, and plays with his sensitive nipples when no one is looking. Kotaro reacts to the pleasure of being sucked and licked over and over again, and although confused by this new experience, he becomes obsessed with her teasing his nipples...