A few years after Chisato gave birth to her daughter as a surrogate. Her relationship with her son-in-law naturally ended, and she returned to her life alone. Just then, her younger sister and her husband appeared in front of Chisato with solemn expressions on their faces. They asked Chisato to give birth to her as a surrogate, just like they did with her older sister. Chisato was overcome with despair, but she had no choice but to nod, not wanting to see Muzu's sad face. The daughter then asked her mother Chisato about her period and checked the possible day of conception. The three of them were in the bedroom, all nervous. As the daughter watched, Chisato and her younger sister's husband began to have sex. Chisato knew she shouldn't feel anything, but she was numb again by the sexual encounter with the young man. As she received her son-in-law's sperm inside her, she felt a sexual desire welling up inside her. The baby was successfully implanted, and the younger sister and her husband had a healthy baby. Chisato was watching them, but her eyes were on her younger sister's husband...