Yuki, who lost her husband, lives with her son, Hisashi. One day, she notices that her son's penis is getting strangely erect. Yuki is aroused by the rock-hard cock, which resembles her late husband's, and decides to calm it down with her own body. She makes Hisashi cum on various parts of her body - her hands, feet, breasts, and her prized ass - but Hisashi's penis shows no signs of going limp. Before she knows it, Yuki decides to use her vagina to take her son's virginity...