My sister is a strong and cute fighter. She has a tomboyish personality, so I always have to join her in martial arts practice. My athletic sister's libido seems to increase when we spar, because she straddles my dick and satisfies her overflowing desire with a powerful cowgirl position. I'm a sexual punching bag... This continues every day, and I finally got fed up, so I made my sister understand by thrusting hard until she cums and rebelled against me, cumming inside her over and over again!