My sister suddenly visits my room. She says she doesn't understand her studies, so I help her, but she gets tired and falls asleep. While she sleeps, I start to feel aroused and begin to play a prank on her without her noticing. I become so engrossed that I didn't notice she had woken up! Seeing this, my sister suggests, "Just rubbing, okay?" It was supposed to be just that, but...?
