Yukari, a serious mother with little sexual experience beyond her husband, catches her adult son masturbating and is shocked by his ability to ejaculate repeatedly. A friend jokingly claims mothers normally help, so the overly earnest Yukari dresses provocatively and gives her confused son handjobs and blowjobs. The insatiable adult son grows attracted to the mother who keeps making him come, eventually pins her down, crosses the line, and creampies her. Even after learning the advice was a joke, it is too late: behind her frequently absent husband’s back, mother and adult son begin having sex whenever desire strikes, and she comes again and again.