Nier's ass, a masterpiece of robotic engineering, is the centerpiece of their forbidden tryst. 9S's mechanical fingers spread her cheeks wide, revealing her tight, glistening hole. He slides a thick, black plug into her, stretching her as she gasps, her pussy dripping with lubricant. She grinds against the plug, her ass bouncing, as 9S watches, his cock throbbing with desire. He can't resist any longer, replacing the plug with his cock, fucking her hard, the sound of their mechanical parts clanking in rhythm with their fucking.