Yuko discovers her feelings for her son go beyond those of a normal mother when she catches him masturbating in his room or finds herself cast as the heroine in his erotic stories. Confiding in her friend Reiko, she is shocked to learn Reiko has also been secretly watched while masturbating by her stepson—and eventually engaged in a physical relationship with him. Inspired by Reiko's belief that "a mother is a being who accepts everything," Yuko resolves to finally become lovers with her own son.