Sagimiya Shun lives with his mother Hazuki, older sister Kaguya, and younger sister Misaki. As he grows older, he is sexually attracted to them. The Sagimiya family…that is a family that lusts after those with the same blood. Or rather, the cursed blood of Sagimiya lusts only for members of the same clan.
One day, his relatives start living at his house, a boy and his mother with a voluptuous body. Days later, he accidentally sees them having sex. Having tried to live a normal life until then so that everyone won’t be unhappy, how will this new development change his relationship with his mother and sisters?
Is not being unhappy by having self-control good enough? But how long can that really last knowing he has Sagimiya blood? Shun, who finds living a normal ordinary life abnormal, is beginning to wonder if happiness for his family means living an abnormal life.