Although she is married, Reiko spends her days in frustration, with almost no sexual relations with her husband. In contrast, her step-son Shinji has a strong libido, and every time she enters his room, she gets turned on by the masculine scent he gives her... Then one day, when Reiko witnesses him masturbating, she can't resist his manly, erect cock, and strokes it as he asks. However, Shinji, who has an insatiable sexual appetite, can't resist after ejaculating once, and even though he has just ejaculated, he continues to show off his erect cock...