Thinking of his stepmother Kogiku, who seemed lonely without her husband around, the brothers decided to have an affair with her.
Several years ago, Tsukishima Kogiku married a man with children. Her two stepsons adored her like their real mother, and the household was filled with a warm atmosphere. Then, her husband's overseas assignment was decided, and he told his sons, 'You must help Kogiku if she's in trouble' before leaving. Feeling lonely without her husband, Kogiku indulged in self-pleasure alone. Seeing Kogiku's lewd behavior, the sons felt they had to help their stepmother.
