Tutomu was obsessed with masturbating every day and showed no interest in anything else. Seeing her son like this, Chisato grew deeply concerned. One day, Tutomu came home from school injured. When Chisato asked what happened, he said, "I got into a fight after being laughed at for scoring zero on a test." Hearing this, Chisato decided to personally use her body to teach Tutomu, determined to prevent him from suffering further humiliation.