Yuya and Sumire are a married couple living happily in Tokyo. Sumire's younger sister Mitsuha, a college student, is staying with them. Mitsuha is a beautiful girl with a flaw, and a certain thug has set his sights on her and tricked her into a pseudo-romantic relationship. The man who plays Mitsuha's boyfriend, Hinata, is a member of a semi-criminal organization, and together with the others from the organization, he sets his sights on not only Sumire but also Sumire, and before long, he repeatedly commits gruesome cuckold sex in front of Yuya. After nine months of humiliation, the sisters' stomachs eventually...