The wife lives with her husband and father-in-law. She married her husband because she was attracted to his seriousness, but he is always working and they have no sex. She is attracted to her father-in-law who is kind to her at times like these. One day, the wife learns from a news story that her father-in-law and her husband have the same blood type. "If we have the same blood type...but..." she hesitates, but immoral thoughts come to her mind. After her husband comes out about his dislike of children and she sees her father-in-law masturbating with her underwear, the wife makes up her mind and seduces her father-in-law and has a relationship with him. From then on, like a kite with a broken string, they have an affair over and over again, and finally... they engage in an immoral, forbidden incestuous pregnancy-inducing mating.