Yumi felt lonely due to her husband's sudden business trip, but she enjoyed spending time with her son. One day, she accidentally saw her son's morning erection and realized that his penis was much larger than her husband's. Yumi, who had always been into big penises, couldn't stop thinking about her son's from that day on. Eventually, she couldn't hold back anymore... and ended up taking her son's virginity. Knowing it was wrong, yet becoming more and more addicted to big penises...
