Naoko and her husband, who are remarried, each had a child from before. Three years after remarriage, when the couple became sexless, her husband's stepchild began to be interested in Naoko's plump body. Her frustrated Naoko is overwhelmed by her sexual desire, which is filled with her stepchild's "attachment to her mother", and treats her sexually. Then she hid in her family and nurtured a physical relationship with her stepchild.
