I thought my step-sister, who was born from my parents' remarriage, was doing something in my room, so I secretly peeked in, and to my surprise, she was masturbating with the legs of a kotatsu table inserted into her pussy, feeling so good! I was so surprised by the sight that I couldn't take my eyes off her, but my step-sister found me, and it was an awkward atmosphere... I tried to lecture her about masturbating in someone else's room, but with my crotch fully erect, it wasn't convincing at all! Maybe she was horny after seeing it, or maybe she was embarrassed and angry, but my step-sister grabbed my dick and asked me to teach her how to have sex properly...