"Dude, fill my ass until I'm projectile vomiting your cum "

She smiles and finishes getting undressed, throwing her clothes unceremoniously in a pile by the door. She jumps on your bed and flattens herself, rolling around and getting all of her wet in your goo. You follow her, getting of your knees and holding your cock. She flops onto her belly, dipping her mouth down to slurp up as much cum as her head can reach. Her plump butt cheeks are covered in your cum, and begging to be spread.
You grab a cheek in each hand, and take a moment to massage and play with her ass while Mia has her breakfast. After grabbing and spreading her fat cheeks around for a little bit, you slide on top of her and place your cock as her ass' entrance. Your pre made the initial bump a breeze. You slowly began to thrust, pushing in more of your meat inches at a time.
"I cannot believe I'm here doing this... This is our biggest fantasy, and all of a sudden it's just... real!" She says.
"I can't believe it much, either. But now that it's a reality, what else is there to do but live?" You reply. Mia doesn't reply, reserved to licking at your mattress and pushing down on it every so often to get it to ooze out more. By now you had gotten all of your length in, and were hilting her rapidly with each pump. The room soon filled with the sounds of both of your moans.
You bend over and shakily pant out, "I'm close."
She smiles and replies through her moans, "You know what I want..."
You sped up, jackhammering her spongy soft hole until once again, your dick took your mind hostage. You hilt as your balls roar. Your body is awash with euphoria as your cock injects rope after half-gallon rope inside Mia. Three ropes and her guts were full, another and her stomach was bloated with it, all subsequent ropes came out of her mouth in gloopy retches. Four minutes of straight orgasm, and four minutes of Mia throwing up your cum. Once you were finally done, Mia still needed a couple more retches to be able to breath. She coughed and hacked, gulping in precious air. Her belly was immensely bloated, unable to accommodate any more cum. She smiled and relaxed into her pool of cum vomit, idly sipping at it while waiting for you to come to. Her ass instinctively tried to shit out the immense blockage in her guts, but your cock was such a thick plug nothing managed to get out.

After another two minutes, you woke up to a heady afterglow and your cock still stuffed deep in your best friend's guts. You smile and pull out, causing Mia's body to begin desperately pushing out the immense mass within. it was a consistent flow, with occasional strong spurts.
"Yo. This won't stop for a while. Watcha wanna do while we wait for that to get shat out?"