Dark bedroom, door cracked open just enough. His sister is on the bed, legs wrapped around the stranger's waist, moaning loud as he thrusts deep and steady into her soaked pussy. The guy grips her hips, slamming harder, her tits bouncing with every stroke. She gasps his name, nails digging into his back, begging don't stop. He flips her doggy, pounds from behind, ass rippling loud slaps echoing. She cums hard, shaking and screaming, pussy clenching tight. The watcher strokes himself silently in the shadows, breathing heavy. Guy pulls out and blasts thick ropes across her back and ass while she pants, oblivious to the eyes on her.