My step-sister, who I ended up living with after my parents remarried, is so cute and has amazing boobs... I'm going to take advantage of our relationship and have her all to myself! I was so excited about this anime-like development, but she said, "Big brother? Gross... We're not related by blood, are we?" She blatantly hates me... But one day, I looked into her room and saw my sister masturbating... From that point on, we crossed the line and became like close friends with benefits. We're not related by blood, so it's okay to have sex, right?