He fingers her ass

Nick quickly coated his finger in the combination of his precum and her fluids, and pressed it against her rosebud. It opened, and his finger slipped inside. Jessie moaned, but started to protest, "Nick, I-"

"If you tell me to stop, I will." He said it as though he was reassuring her, but really, it was a threat. She fell silent, and he rubbed her back with his other hand. "Good girl."

She blushed, annoyed at how much control he had over her like this, and bit his shirt again, so that he wouldn't get the satisfaction of hearing her moan. This was the third, no, fourth time he had put a finger in her ass, and the first time she had asked him to stop, and he had. She had never managed to tell him to stop again.

She couldn't help but fear the day when he inevitably fucked her ass for real. She dreaded it so much, in fact, that she sometimes had nightmares. The kind of nightmares where she woke up with a soaked pussy.

Nick didn't have a thing for butts before meeting her, but he loved the control it gave him over her, the way she couldn't resist him when he touched her there. It was time, he decided, and curled his finger. "Cum for me." he whispered, and he finally got his own release, pumping her full of his semen. He smiled as he listened to her suppressed moans come out as soft whines as she came with his finger in her ass. "Good girl."