Elasticity

With Sara grinding atop him, Josh quickly tried to come up with a new rule that he hoped would work.

Women's assholes are elastic enough they stay tight no matter how much they're used, he typed.

"What the fuck are you unnngh doing back there?" Sara demanded. "Are you ohhhh texting?!"

"Emergency email from work," Josh claimed.

"Hurry gaaaah up!"

Inspired and pretending the email needed a longer response, Josh also typed, Tramp stamps are as common on women as pierced ears. Sara had pierced ears, so he assumed this would give him a decoration to look at while taking her from behind from now on.

He tapped the "enter" button and then put his phone back down on the bed. "Okay, babe, I --"

There was a flash, but it wasn't as disconcerting as before, when Josh had changed more rules. Sara's lower back now sported a colorful tattoo of several butterflies and curlicues, he saw, and then he realized that his cock was in a much tighter space.

"Oh, fuck," he said, with both the brand-new physical sensation, and the feeling of power -- had he really, on a whim, just given sexy tattoos to millions if not billions of women? -- combining to send him over the edge. "I'm gonna cum!" he warned.

"Me mmmph too!" exclaimed Sara.

Josh tried to pull out so he could see his cum on Sara's ass and her tattoo, but she was tight enough that he couldn't. "Oh, god, oh, god, oh, god," he moaned as he felt himself delivering several pumps into her anus. She uttered something halfway between a moan and a scream. Josh could see her toes clench.

He was finally able to release himself as Sara leaned forward, breathing heavily as she positioned herself to keep Josh's fluids from staining the bedsheets any more than they were already stained. A bit did leak out, though, but she reached over to one side of the bed and picked up a blue plastic butt plug, grunting a bit as she inserted it.

"That was awesome," Sara said as she raised herself up and swung her legs over so she was sitting on the side of the bed. "Got a lot better once you weren't distracted, right?"

"Yeah," said Josh, taking deep breaths himself but finding it hard to relax with this enhanced version of his girlfriend still sitting nude in front of him.

"Of course, since you were emailing while you were supposed to be giving me all your attention..." Sara trailed off and looked meaningfully down at Josh's crotch.

"Uh, what?" asked Josh, realizing that he could feel blood rushing back to the area she was gazing at, thanks to the one-minute refractory period he'd given men.

She looked back up into his face, said, "You owe me a favor," and licked her lips.