As the daughter of my father's second wife, I became my stepsister's "Momo." Unlike me, who stayed at home, she was a sunny and cheerful person, treating everyone with openness. However, because of her overly open personality, she didn't treat me like a man at home, living without any defenses, completely exposing her buttocks in a thong. Having never seen a hairless butt before, I continuously contemplated lewd things about my stepsister's buttocks. One day, I finally reached my limit…