Agree with Amy, then use her

The opportunity presented itself all too easily. It would only take a few words from you, and Chris would become a pervert in Liz’s impressionable eyes, at least for a while. That’d open up lots of possibilities... You could deliberately expose her in front of Chris, just to feed her distrust of him. Not only would that make for some amazingly kinky sex, but it’d also serve to make Liz a wedge that you could drive between Chris and Amy.

Unfortunately, you think that a plan like that might go against the intended nature of this new world. Charles and the doctor may not take it too well if you try to meddle with their experiment. Not to mention that doing such a thing comes with the risk of creating tension between you and Amy, and that’s the last thing you want.

“Your sister is right, Liz,” you say, glancing at Amy. She gives you a grateful look, and with great difficulty you flash her a half-hearted smile. “You’re covered in my cum, anyway. He probably knew what was up the second he stepped in.”

“Right! You gotta remember that John comes by pretty often,” Amy says, nodding enthusiastically. “This isn’t the first time Chris has seen me or some other girl sitting around naked and drenched in cum. It used to freak him out at first, but now he just knows it’s just part of having John around.”

Liz’s frown lifts slightly. “Really?”

“You know I would never lie to you,” Amy assures her sister, giving her a hug. You grin as the sticky cum on Liz’s breasts gets stamped onto Amy’s chest as well. “You just have to get used to it, girl.”

“...You might be right,” Liz replies uncertainly. “I just have to get used to it. Gotcha.”

“I’ll help,” you offer with a lecherous grin. “I’ll take your address from Amy here, then drop by a couple times a week. You get experience, and I get to fuck a total hottie.”

“Sounds like an excellent idea,” Amy adds.

“Um... Okay," Liz says, going red under your gaze. "Well, I-I should get going. Thanks, John. Seeya, Amy.”

Still blushing, she puts her shirt on over your almost-dry cum and scurries away. She looks back and smiles at you, before disappearing out the door.

Amy sighs, resting her pretty head on your thigh. “You’re so sweet, helping me deal with Liz. I don’t want her having misunderstandings.”

“Don’t mention it,” you say, feeling bitter inside as you fake a smile. “What are friends for?”

“No, really,” Amy refuses with a shake of her pretty head. “I owe you one.”

“Fine. You can buy me lunch or something,” you concede. “But for now... I’m hungry for something different.”

You flex your cock, and it jumps into her view. She gasps is shock, then grasps the sensitive organ in her hand.

“How are you still hard? You just came,” Amy says, surprise visible in her eyes as she brings her other hand up to cup your balls. “Wow, your cock feels... Bigger, somehow. And these are still so heavy...”

You wordlessly lean down and push her onto the floor. She yelps as she falls, then giggles when you crawl up her body, kissing her every few inches.

“No--That tickles,” she chirps as you brush your lips against her smooth stomach.

As you lift your head to gaze down at her, she's biting down on her bottom lip sexily and gazing back with fire in her eyes.

“This is more like the John I know,” she whispers, hooking a leg around your hips. “Forcing me against whatever’s close and just taking his pleasure.”

“You make me sound like a brute,” you reply, reaching between her legs and searching for her entrance. You smile when you find it, and begin to pump your fingers in and out of her dripping sex. “You don’t seem to mind, judging by how wet you are.”

“Not your hand,” Amy moans impatiently, bucking her hips. “That's not enough...”

You growl and lean in to claim her soft lips. She returns the kiss with equal urgency, gripping at your hair as she tries to pull you deeper.

You brace one hand above her head and use the other to rub your cock against Amy's slit, lubricating it with her juices. Once your cockhead is slick enough, you place it at her entrance and begin to lower your hips. You meet a little resistance, but you **** it into her just like last time, letting out a groan as you’re engulfed by Amy’s wet, slippery warmth. Then you hook an arm below her knee and **** it up, raising Amy’s hips into an ideal angle for thrusting.

“Mmmh,” she moans hotly into your mouth as your glans brushes against her moist walls on its way deeper inside.

You feed inch after inch of your cock into her tight cunt, letting out grunts of approval as more and more of your length is embraced by her folds.

"Oh, gosh..." She gasps with pleasure as the last inch is buried inside her, and trembling under you.

You nibble at her bottom lip, firmly grasping her hips as you begin to slowly thrust into her.

“Oooh, John,” Amy moans, legs locked around your hips. “Harder!”

“Fucking slut!” You comply, picking up the pace. "Take it!"

“Yes! That’s it,” she gasps, a wild expression on her face as you pound into her cunt. “Just like that! Fuck me!”

“Take it, Amy! Your boyfriend can’t give you this,” you growl, singlemindedly trying to push her over the edge.

"You know he can't!" Her moans grow louder and louder with every thrust, and you find holding your orgasm off increasingly more difficult as well.

“I-I’m,” she gasps, **** on her words. “Cuh-cumming..!”

Just as the words leave her mouth, you grunt and bury yourself inside her, no longer holding back.

“Aaaahn!”

Amy writhes briefly yet violently beneath you as her orgasm hits, then goes limp while you dump your sticky load deep inside her. You groan in satisfaction while her cunt milks your cock... And even after you've pumped out every last drop, you're still rock-hard.

A couple of minutes pass as you lay on top of Amy's body, listening to her breathe and gasp softly as she comes down from her high. She then crawls out from underneath you and starts to crawl towards the couch on all fours.

Seeing her bubble butt wave in the air with your thick seed dripping out of her pussy, you gulp as you chase after her quickly.

“That was... Amazing,” Amy sighs, reaching out to the couch. “Now, let's get you that lun- eek!”

You drag Amy back towards you and thrust your cock into her once again, and the friction against her sensitive cunt is too much for the poor girl. Her eyes roll up into her skull for a second as the air goes out from her lungs.

"I want to spend the day inside," you say leisurely, lightly patting Amy's buttocks as she regains her bearings. "And inside you."

“R-really?” Amy looks up at you with a awed expression once she regains her senses. She seems eager to continue, but hesitates. "I'm supposed to watch a movie with Chris in a couple of hours, though. You wanna join us?"