During his teenage years, Tohru was obsessed with his mother, Erika's sexy body! He would peek at Erika in the bath, get his penis erect, and fantasize about her. As his desire escalates, he can no longer be satisfied with just fantasizing, and he ends up playing a prank on the sleeping Erika. But Erika notices. Having been sexless for a while now and feeling sexually frustrated, Erika is excited by her son's pranks.