Several months ago, Shota's mother remarried a new partner, who had a daughter named Hibiki from his previous marriage. Shota instantly fell for Hibiki, his new stepsister, especially her big tits, and became obsessed with groping her breasts. Taking full advantage of the special privileges of being the family's favorite, he indulges in lewd acts with his busty stepsister, while the rest of the family looks on with envy.