The answer that the little sister who desires her brother's body finds is to hide her face with a mask!! Mikoto, a plain little sister who wears glasses, accidentally witnesses her brother's erect penis. The little sister, who has no experience with the opposite sex, cannot get the sight out of her head. Unable to suppress her sexual Kokoro, she disguises herself as a masked slut and attacks her brother. Even though she hides her face with a mask, her brother can easily see Mikoto's true identity!! She is obsessed with penis and appears out of nowhere, reverse raping her brother and forcing him to cum inside her. Even when her brother is exhausted, the little sister's sexual desire is not quenched!!