Naoto Rindo, the successor of the wealthy Rindo Group, must fulfill a family tradition called the Hinotsukisai by impregnating a woman to ensure the clan's prosperity. After failing with his partner Yuiko, Naoto is ordered to impregnate one of Yuiko's sisters—Shino, Ayumi, or Mizuna—within a month or face expulsion from the family. While he attempts to seduce the gentle Ayumi, a traumatic memory of his deceased fiancee, Suzune, resurfaces during their intimacy, leading to a distressing encounter that reveals the deep scars of Naoto's past.