Shingo is a high school student, living alone. He sleeps with many girls ranging from his classmate girls to other school girls. But there is one girl, whom Shingo keeps a close relationship for several years. Her name is Shiori, his ex-homeroom teacher. He still doesn't love her, just a sex friend. One day, Shiori says to him, "What about living together at my house?" At first, he refuses it but he finally accepts it because he knows she just wants his body. But there is still one problem. That's Shiori's younger sister, Naho. She is his classmate and he hates her but doesn't know why. Naho is beautiful and liked by everyone. The more he sleeps with them, the more he understands them... [From ErogeShop]