One day, Mio discovers a discount coupon from a brothel in her son Takashi's pants while he's bathing. Surprised that Takashi might be visiting such places, she confronts him, only to learn he has no experience with women at all. Touched by his innocence, Mio decides to teach him how to kiss. Takashi, starved for physical intimacy with a woman, can't stop at just kissing and gradually becomes more passionate...