Since her father died early and her mother remarried to someone else, the sisters Miru and Shion have a new family. Miru is an older sister and a lively, intelligent and pure schoolgirl. Shion is the younger brother, she is quiet and somewhat dislikes her new father. Some time later, the mother of the two became pregnant. The stepfather took both mothers to his maternal grandmother's house to facilitate childbirth. Since my mother was not at home. The stepfather always used lewd eyes to look at both sisters. And the first person he attacks is Shion. Taking advantage of Shion's low self-esteem when compared to her sister, he quickly manipulates her emotions, making her listen to his every word. Miru finds out and in order to save Shion, she volunteers as a replacement. But the feeling of happiness that her stepfather brought made her gradually lose herself. Both sisters were gradually brainwashed by him, unable to live without his cock...