Her son, Haruo, is a virgin. His mother, Fumiko, accidentally overhears what he's saying and, due to her daily sexual frustrations, becomes aroused. She plots to somehow take Haruo's virginity, and succeeds in helping him lose his virginity as planned, but... Far from going limp, Haruo's penis becomes even more aroused and asks for a rematch. At first she thinks it's because he's young, but even Fumiko is put off by Haruo's incredible sexual prowess, which gets erect instantly no matter how many times she masturbates. She takes advantage of an opportunity to escape into the bathroom, but Haruo barges in...