a delinquent son and his studious sister who looks down on him. their mother, chisato, worries about their strained relationship. today, they argued about the sister's reference books. after the sister leaves, chisato comforts her depressed son. she gently strokes his head, and he asks if he can be affectionate with her. she agrees, and he starts kneading her ample breasts. unable to hold back, he shows her his hard, erect cock, and she hesitates but reaches for his crotch.