For better or worse, my caring sister is concerned about my inability to study and is tutoring me diligently. She said, "If you get a perfect score, I'll do anything for you," so I studied hard and made her my personal reverse bunny slave! At first she complained a lot, but when I straddled my dick and ordered her to have sex, she started bouncing up and down and cumming like crazy! She became more and more obedient and served me with a titjob with her big tits exposed! For the past three days while my parents were away, I had sex with my bunny sister, whose positions and exposure were reversed!