Since childhood, Hiroto has lived alone with his father. He's always admired his friend's mother, Rieko, who treats him with kindness and care, and before long, he begins to develop romantic feelings for her. Yet inexperienced and ignorant about sex, he finds himself unable to control his growing arousal and ends up confiding in Rieko. Surprised but wanting to help him, Rieko secretly gives him his first sexual guidance. Enthralled by these new sensations, he can no longer restrain himself, pushing her down and thrusting wildly. Overwhelmed by his relentless rhythm, Rieko reaches climax after climax.