It’s hard to pinch yourself mid-fuck, so she had to make do with biting.
Not that it was overly dream-like, that relentless pace hammering between her legs, the way she’d roll her hips backwards to meet him so that, at the apex of the thrust, they’d be so completely flush, his hips against her arse, skin against skin with any bit of air suffocated into non-existence. It wasn’t that she was needing to ground herself. She was just making sure.
Actually, no, that wasn’t it either. it was more basic than that. It was the impulse to throw just one more thing into the pile, until you’re breaking under the weight of it all. She wanted one more sensation. One more thing to push her up and over that edge, so that she could forget about biting, forget about fucking, forget about everything and just blink.
Or perhaps you could just waive it as an oral fixation, the desperate need to do something with your mouth. Maybe she was orally inclined; the faint saltiness on her tongue was a testament to that fact. And the way she was unable to stop her tongue running over whatever bit of flesh her teeth had snagged backed up the idea with a little extra evidence. Her arms, his neck, the backs of his hands; all of them were glistening with little patches of saliva, like puddles after rain.
"Moan." He crooned in her ear, and she knew why she was a biter. At least now, in this moment, she knew why. To muffle, curb, reduce. To give her a little less vocal range and volume, and retain a touch more dignity than she would otherwise.
The reason would change just as fast as that dick thrust between her legs, but for now, that was the answer she’d give to the question that no one but her over-active imagination was asking.