Masae has been frustrated by her husband's lack of sexual relations for a while. One night, she opens the door to her son's room to tell him off for staying up late, only to find him stroking his penis with complete concentration. Seeing his erect penis for the first time in a long time, Masae can't help but imagine herself moaning with pleasure at the sight of her son's hard, thick penis. From then on, she can't stop thinking about her son no matter what she does, so she finally attacks him, aiming for his crotch.