She knew her husband had an adult son, but not how disturbed Kazuhiko had become after his mother left and he withdrew from society. Her sympathy and kindness encourage his obsessive dependence, revealing that he sees his stepmother sexually. He invades her bath, rubs his cock against her, ignores her protests, and eventually forces penetration. Thereafter he assaults her almost daily; she is fucked by her adult stepson during the day and her husband at night. Repeated abuse leaves her unable to think clearly or resist even when Kazuhiko creampies her, yet she remains desperate to avoid divorce.