My younger sister, Hinako, is at a perfect age where she has masturbated but has never had sex. - ``Aren't you wearing a bra?'' ``It's such a hassle.'' My brother finds out that I'm not wearing a bra in the living room, and his abnormal sexual desire ignites and he inserts his cock into the virgin Hinako! - The older brother, who has learned the taste of his younger sister's body, starts playing erotic pranks on Hinako one after another!