Kazuko and her son Satoshi live together in the same house, where Kazuko deeply values her armpit hair. Even during the hot summer, she never shaves it. One day, Satoshi accidentally notices his mother's armpit hair and feels an abnormal excitement he'd never experienced before. From that moment on, he becomes completely obsessed with it, so consumed by desire that he forgets to sleep. Eventually, unable to restrain himself any longer, Satoshi reaches out and touches her armpit hair.