I've been estranged from my sister ever since I passed the entrance exam to a famous high school. One night, I invited Sugai, who is also attending the same high school, to my house and ran into my sister without makeup. That day, Sugai violated her, but she learned the pleasure and blossomed as a woman. I pretended not to see my sister being assaulted and becoming Sugai's sex friend. Today, I get a depressed erection as I hear my sister's moans through the wall.