Fake Cuckolding Becomes Real

[Fuumayami]

A story of a girlfriend and her boyfriend's best friend teasing boyfriend that they are fucking.
I'm thinking boyfriend shared he liked to be cucked. GF and Best Friend don't see the appeal and BF tries to defend it. GF and Best Friend then start teasing BF, sending him pictures of them being very close together without him there. This makes BF hot and bothered. GF and Best Friend keep sending pictures and text messages of their "cheating." It gets to the point that they like this little game they created. Then it gets riskier as pictures of them together gets boring.
How about swimsuits? A kiss on the cheek? Kiss in the lips with tongue, he'll enjoy that! How about you touch my breast? Let's get naked in bed? How about sending him a picture of your pussy and my hard cock close together? Take a picture of me about to swallow your huge cock? Maybe record me having a taste of your wet pussy? Then eventually the inevitable... "Oh fuck your best friend's girl!"
I'm thinking the conclusion will be BF coming in after they had their passionate fuck session and saying, "See... I told you it was hot."

 

[Rob_Royale]

That would work and I think would work great from her viewpoint. From a very monogamous upbringing, she's a little overwhelmed and apprehensive. Afraid he'll use it against her later if he becomes unhappy with the idea.

 

[MikeXIrons]

I'm always a big fan of well-intentioned women finding themselves tempted to be naughty. Nothing better than a slippery slope... where each step seems not MUCH worse than the last... until, inch by inch, she finds herself having crossed "the line" long ago. And, a "game"... just pretending or joking... putting her in a position to start to enjoy the "game".

 

[Fuumayami]

That would work and I think would work great from her viewpoint. From a very monogamous upbringing, she's a little overwhelmed and apprehensive. Afraid he'll use it against her later if he becomes unhappy with the idea.

Yeah, my thoughts exactly is the GF and Best Friend's pov. BF is already set in his ways, we would follow the GF and the things she does with the Best Friend and how this change her. In my mind, BF is just a very chill and confident dude, so he wouldn't try to use anything against his GF.

 

[Fuumayami]

I'm always a big fan of well-intentioned women finding themselves tempted to be naughty. Nothing better than a slippery slope... where each step seems not MUCH worse than the last... until, inch by inch, she finds herself having crossed "the line" long ago. And, a "game"... just pretending or joking... putting her in a position to start to enjoy the "game".

Definitely. And I think it happening "casually" with BF talking about it, opening the gates, just makes it all that more arousing.
There can be more than pictures and texts. They hanging out, watching TV, BF notice GF is cozying up to Best Friend, they even have a blanket over them, "what are they doing beneath it?!"
BF comes home, notice them splitting up, his best friend has his hands in-between his groin as if he's zipping his pants and his GF is wiping her lips and giving him a smirk, "What were they just doing before I came in?!"
He ask GF what's up, she smiles and simply say something along the lines, "maybe we're doing it, maybe not." Which makes him groan in annoyance and arousal.

 

[MikeXIrons]

Definitely. And I think it happening "casually" with BF talking about it, opening the gates, just makes it all that more arousing.
There can be more than pictures and texts. They hanging out, watching TV, BF notice GF is cozying up to Best Friend, they even have a blanket over them, "what are they doing beneath it?!"
BF comes home, notice them splitting up, his best friend has his hands in-between his groin as if he's zipping his pants and his GF is wiping her lips and giving him a smirk, "What were they just doing before I came in?!"
He ask GF what's up, she smiles and simply say something along the lines, "maybe we're doing it, maybe not." Which makes him groan in annoyance and arousal.

And, it could all start out totally innocently.

A married woman at work once, while totally distracted with reading a document, when I left the room said, "OK, thanks, hon". She was immediately embarrassed, having called me by her pet name for her husband. I quickly replied, "No problem, sweetheart", which made her even more embarrassed. I managed to turn it into an ongoing flirtatious thing... something that never could have happened without her initial mistake. Now, when I called her "sweetie" or "hon", etc... I was just teasing her about the mistake she made. I'd throw in an occasional obviously-over-the-top pet name like "Pookie Bear" to make sure it was all just for fun. It never led anywhere but a little fun flirting, but...

...in your story, it could. So, the girlfriend mistakenly calls the BF's friend by a pet name... maybe he was walking into the apartment and she thought it was her BF coming in? Maybe she even mistakenly went a little further and, while in the shower, called out, "Hey, hon. Glad your back. Come join me and wash my back before your friend gets her.".

The friend says, "Sure thing, be right in!". She recognizes his voice now and squeals with embarrassment.

The BF arrives just then and she's totally embarrassed about the mistake and all three of them have a big laugh about it.

The friend teases the BF about how he should leave since the GF invited him into the shower. The BF (mostly) jokingly acts jealous. The GF says "I thought he was YOU!". There's joking about how easy or hard it is to confuse the two of them. The friend jokes that that's why he recently got his hair cut shorter... hoping she'd mistake him for the BF some night.

And so, with that joke established, the friend keeps bringing it up as a joke, happy to have an excuse to flirt with the hot GF. The GF plays along, blushing but appreciating the attention.

The BF plays along, acting jealous about it. The GF blushes and reassures her BF that she'd never knowingly cheat on him... but... mistakes are mistakes, ha ha. But, she makes it up to him with some extra loving... which the BF likes, so is willing to keep playing along with the game.

And the slippery slope begins... advancing from silly verbal jokes... to a little innocent touching here and there, "Ooops... I thought he was you!" Or the friend initiating it, jokingly saying in a bad imitation of the BF's voice, "Hi sexy, it's, me, your boyfriend. Let's get naked". Ha ha...