After 6 years of living apart due to the death of their parents, the Himenokōji twins, Akito and Akiko, are finally reunited when Akito desires to live as a member of the family once more. Although things are fine at first, Akiko begins to express her incestuous love for her older brother, who only sees her as his little sister. Things become more complicated for her when more girls move in with the siblings.