AIKA is a flashy but homely wife who has been married to a man who has a child. He had a good relationship with his son-in-law and lived in harmony with them, but one day he was nailed to the erected crotch of his breath, which he had never been aware of until then. AIKA sees her husband's stepchildren as "the opposite sex" after seeing a big one that is fascinating. Then the distorted affectionate relationship of incest with the breath began.