Nao Takanashi has long been trying to tempt her brother, Shūsuke, into entering an immoral (i.e. incest) relationship with her, with Shūsuke barely being able to resist. Nao goes to great lengths for Shūsuke to think of her perversely by doing things such as letting him purposely look underneath her skirt (and once letting him see her completely naked) but then she always gets him into trouble afterward so as to make it look like Shūsuke is the immoral pervert. One day, while Nao searches through Shūsuke's room for his collection of porn magazines, she then finds a hidden family photo album and is surprised to find out that there are no childhood pictures of her in it. After Shūsuke was finished being scolded about his porn collection, Nao confronts her parents, Shūji and Nanaka, about the album. They then tell her the truth: 10 years prior to the story, a car accident killed Nao's real parents and left Nao with memory loss, so Shūsuke insisted that Shūji and Nanaka adopt her into their family where he vowed to care & look after her as his sister. Nao, curiously enough, is more shocked by the fact she and Shūsuke are not actually blood related. At that instance, Nao realizes that a possible intimate relationship with him would be acceptable. Nao then requests Shūji and Nanaka to keep the fact she learned the truth from Shūsuke so that they can retain their sibling status.
高梨修輔は、年ごろの妹をエッチな目で見てしまう、ちょっと危ない少年。
そして妹の奈緒は、修輔のことが大好きで、自分のことをヨコシマな目で見るお兄ちゃんに“ホンホン”してしまうという、とても危ない女の子。
表面上はごく普通の妹として振る舞いながら、わざとパンツを見せたり抱きついたりして修輔を誘惑し、彼がドギマギする様子を楽しんでいた。
ある日、掃除するという名目で修輔の部屋に入って彼が隠しているエロ本をチェックしていた奈緒は、そこで思わぬモノを発見してしまう。
Nao Takanashi ha intentado por mucho tiempo tentar a su hermano, Shūsuke, para que entre en una relación inmoral (es decir, incesto) con ella, y Shūsuke apenas puede resistirse. Nao hace todo lo posible para que Shūsuke piense en ella perversamente haciendo cosas como dejándolo mirar deliberadamente debajo de su falda (y una vez dejándolo verla completamente desnuda) pero luego ella siempre lo mete en problemas para que parezca que Shūsuke es el pervertido inmoral.
高梨修辅,好色的眼睛看到了妹妹，陷入危险的少年。修辅的妹妹奈绪，喜欢用自己天真的眼睛看着哥哥，做各种大胆的手段，非常危险的女孩。表面上是非常普通妹妹的举止，却故意露出内裤，看着修辅慌张的样子，享受着。有一天，以打扫的名义，在修辅的房间，对他隐藏的色情书检查的奈绪，在那里发现了意想不到的东西。
