Adopted into the prestigious Hiragi family as a child, he was led by the protagonist Kuuya's older sisters, who led a weak life, and he was left in the care of a distant relative in order to retrain his sexual strength. And about 10 years later. Kuya grows up nicely and returns to the Hiiragi family. Even though he is his younger brother, he is an adopted child, the only male, and he has started a life surrounded by six older sisters.