Yoji consults his mother-in-law Mari about his wife's infidelity. Yoji, who is interested in Mari's large breasts, brings up the topic of infidelity and steals a kiss from her. He tries to push her away, saying he can't do such a thing, but Mari, who has not had sex with Yoji, resists Yoji's advances and yet gives in to his advances. And so their relationship becomes deeper...