After remarrying Tooru, Sakiko strives to become a good stepmother to his son, Kaoru, in their new household. However, Kaoru feels uneasy around her, drawn less to her maternal role and more to the strong pheromones she exudes. One day, returning home from school, Kaoru sees Sakiko chatting cheerfully with a delivery man and suddenly loses control, exploding in anger. From that moment on, Kaoru stops seeing Sakiko as a blood-related mother figure and begins treating her solely as an object of sexual desire.