Mark struggled against his restraints, but he couldn't budge. The knots holding his wrists behind his back, and his ankles to the chair, were tied well.
In front of him on the bed, bent over on all fours and facing him, was his beautiful girlfriend, Erin. And behind her was Jason, Cassi's boyfriend. He was a former college football player with huge shoulders and washboard abs. He had his hands wrapped around Erin's tiny waist and his cock buried inside of her.
This wasn't what Mark had wanted when he had suggested a foursome. He tried to protest but could only let out small muffled sounds against the rag stuffed into his mouth. Cassi, Erin's best friend - and the person responsible for orchestrating Mark's current predicament - laughed. She was on her knees, pumping her hand up and down Mark's stiff cock.
"Oh wow, do you see how good your little girlfriend looks getting bent over and fucked by my boyfriend's big cock?" said Cassi. Still pumping her hand up and down.
Mark let out a groan. He didn't want this, but he'd never been so hard in his life. Watching the love of his life getting stretched out by this meathead's massive cock was doing things to his mind that weren't natural.
He watched as Erin cried out in pleasure. Her eyes rolled back in her head as Jason methodically hammered his big cock into her like she was an object that needed to be penetrated in a certain way to get an orgasm out of her. She was no longer even aware that Mark was in the room. Her moans and whimpers filled Mark's ears as she gave her body to the man enthusiastically. Jason took the cue and picked up the pace of rhythmically driving his cock in and out, a piston in perfect motion.
Cassi simultaneously slowed her speed of pumping Mark's cock. She drizzled some more lube over the tip and gave him a knowing smile. It was the cruelest thing Mark had ever seen.
"Oh my," she said, looking back over her shoulder. "Look at Erin turning into a little slut for my boyfriend. She's never experienced this much pleasure before, has she? You're never going to be able to satisfy her again after this."