Four wives are drawn across the line by their fathers-in-law. Eri, frustrated with sex with Keita, discovers sensations she has never experienced under his father's meticulous caresses. Shy Mayumi trembles at the slightest touch before his persistent technique overwhelms her. Yui's father-in-law changes toward her after discovering the debt she hid from her husband. Hana sees his erection while washing him and impulsively offers to clean below as well. Their bodies and loyalties gradually give way to the older men's intense sexual skills.