The machine's hum vibrates through the room, an ominous symphony of impending pleasure. The man's ass cheeks clench, then relax, as the machine's strap-on pushes past his tight ring, filling him completely. The instructor watches, her eyes gleaming with sadistic satisfaction, as the machine's piston-like movements milk the man's prostate. He gasps, his body tensing, as waves of intense, overwhelming pleasure crash over him. His cock twitches, spilling cum onto his stomach, as the machine continues its unyielding assault, pushing him beyond the brink of ecstasy, again and again.