Ai and I are not actually siblings. When I was a student, my father remarried and Ai was his stepdaughter. A year later, my parents passed away and Ai became my parent figure. As we spent our days alone together, I began to feel a special affection for Ai, my only family member. Just as I was swearing to myself that I would make Ai happy in the future, my bad friend Shinji approached our family. "Your sister is pretty sexy and beautiful, isn't she?" he said, and started hanging out at my house...