Wishes for nothing more than a proper family life as Kyousuke's step-sister. When she lived with only her ​​mother, she was mostly alone at home because of her mother's work, but with the new marriage, she now has both a father and a brother and her loneliness is that of the past. After the death of her stepfather, Kazuma, she is now terrified that the family will break due to Kyousuke's grudge against her mother. To keep her family together she is willing to do anything Kyousuke asks, with the deal of only her virginity remaining untouched. Their relationship takes on a very intensive form as they match Kyousuke's sadistic tendencies, which developed even more masochistic preferences.