Her only son believes he's unpopular with women because he resembles his father. Feeling sorry for him, his mother—driven by overprotective instincts—ends up helping him masturbate. As a result, a forbidden relationship begins to form between Yuu and her son. Their intense sexual desires deepen, eventually escalating to full intercourse. Despite knowing it's wrong, she loses her virginity to him. From that moment, Yuu becomes increasingly drawn into her son's throbbing manhood. Their taboo bond transforms into something impossible to stop.