I was forced to assist my sister, who started doing butt training, with her workouts... At first, I had no interest at all, but I gradually got excited as my sister's butt grew bigger and bigger. I was captivated by her huge butt sticking out during her butt training, and I couldn't resist but to press against it from behind! My sister, who was initially surprised and resisted, began to twitch her anus and started to feel it. I got extremely excited by her black, tight, and bulging butt like a foreigner's and repeatedly thrusted hard, resulting in continuous ejaculations!
