Miyuki, a beautiful high school girl who is well-known at school, has a perverted brother who is always hiding in her house and peeping on her when she masturbates or when she brings her boyfriend over and has sex with him. One day, the brother sneaks into Miyuki's room and fails in his usual nighttime seduction, and from that day onwards he becomes his sister's slave, and his sister treats him like a butter dog on a daily basis, forcing him to perform cunnilingus on her... Such a brother and such a sister!