Agree

"Fine! But at least set an actual time!"

You snap back at Kevin after a moment's thought. If you're going to play his game, you might as well make sure you can win.

Snickering, Kevin leans down across you, his mouth getting close to your ear as he presses his chest to your back.

"Sound good to me. We'll cap it at three minutes. Clock over there just hit the minute mark. But if you lose, I want you shaking your ass for me while I'm inside of you."

You nod with gritted teeth, feeling goosebumps from having Kevin practically whispering into your ear. Is it really so fun getting close to another guy? Though, you're increasingly suspecting he's not seeing you as a guy at all anymore...

In any case, it's only three minutes...you can clench that long. Kevin's cock is pushing pretty insistently at your entrance, but there's no way you're letting him in.

A minute passes on the clock, and you're increasingly confident of victory. Kevin's surprisingly keeping up roughly the same amount of pressure on your sphincter, not cheating by ramping it up over time, and you're only just barely starting to feel some strain.

The situation is far from pleasant though...Kevin's cock is practically glued to your ass, and he's got a lot of his weight on your back while he grips your shoulders for balance. You're uncomfortably aware that he's a pretty big guy...if he takes back his promise after losing, there's no way you'd be able to pry him off you.

Another minute passes, and you grow more secure in winning. Two minutes of clenching is enough to make you confident of holding out for another minute...