When I saw my younger sister, who hadn't spoken to me in years, forced to have sex with a playboy, I felt like I'd been stolen from her, and I couldn't stop the traumatic erection. (Miyajima Ume START-301)

After I got into a prestigious high school, I drifted apart from my sister. One night, I invited Sugai, a student from the same school, to my house, only to bump into my sister, who was without makeup. That day, Sugai was raped by my sister, and after experiencing pleasure, she began to blossom into a woman. I saw my sister being raped and becoming Sugai's sex partner, but I pretended not to see it. Today, I heard my sister's moans through the wall again, and I got an erection.