You stand there huffing after your orgasm as the large man starts to walk your way, hand still firmly stroking his cock. Your erection comes back full force once he is standing right behind you and begins to run his free hand down your spine, smoothing down the hair on your back until his hand reaches your ass and he gives it a firm squeeze.
You begin braying loudly at the squeeze and while distracted, he walks around to the front of you, gets down on his knees, and stares up at you with hunger in his eyes. Your new part beast part man brain sees this and immediately decides you NEED to put your thick donkey cook down this ripped mans throat right then and there or you are going to explode. You thrust forward suddenly and force your cock past his lips which he gives a receptive moan at. His mouth is soft and warm and PERFECT for shoving in and out of. You had no idea how he took so much of your huge cock into his mouth but god that hot wet maw was doing exactly what you needed done and soon you spray so much of your cum down his throat that when he pulls back he has cum dripping down the sides of his face with a dopey smile and lust in his eyes.
Almost instantly he started to smell better to you and you could immediately see exactly why. The muscular man sits splayed on the floor while his cock now starts throbbing bigger and BIGGER before your eyes. His face is completely bilssed out as his balls swell to 10x their original size and his cock stretches further and further until it is huge and sporting a flared head.
You look down at him and are drawn to his new hot and masculine smell. You wrap your lips around his cock and watch as your face begins to strech further and further out into your huge new muzzle that you take more and more of his cock into your mouth with. While you greedily suck him off, hair begins to fizzle up from his groin and makes its way up his swelling body. His ears strech to match yours and he now hears your light grunts and slick noises from around his cock and god was it somehow making his cock swell even more.
A ropey tails slithers it's way out of his spine and you grab hold and pull HARD eliciting an excited "HEHAW HEEEEEE HAWWWWWW" from your partner who clapped his hands over his mouth in shock and pulled himself up off the floor a bit like a trance had been broken as he started to try to run. (Un)fortunately for him his feet started to crack and reform into big, study hooves that sent him face first into the floor. He lay there, sprawled across the floor, thick chest heaving with arousal and fear, and thick grey fur rising to cover all of his hot muscular body.
You take this as your chance to finally get the fucking you desperately need and get down on all fours while shaking your ass a bit and lifting your tail to call him over and by god does it hit him like a truck. He stands up slowly as he tries not to fall over again and makes it right to you before tripping and landing face first into your ass.
You bray in your excitement as he takes in you scent and begins to lick your hole, getting it nice and stretched for his cock that was now straining so hard it hurt. His face began to push out further and further as his tongue grew thicker and longer, and he took this advantage to really ram it into your opening. You feel your hands start to tingle just like your feet earlier and feel excited at the beast you are about to be pounded into. He finally pulls his now fully donkey face from your ass and inhales once more before plowing his cock full force into your waiting and ready hole.
You almost scream as his larger than life cock pierces your ass and you are in heaven after he begins to rub it back and forth inside of you. Above you he is panting, moaning, and drooling as his beastial brain has taken over front seat and is making him jackhammer into the tight wet hole you ever so graciously presented him. His rippling body felt like it was melting from the heat of you as his hands cracked and snapped into his new hooves that he laid over your sides for a better grip as his body began to surge larger in size.
"F- FUCK, GIVE IT TO ME HARDER YOU SEXY BEAST HEEEEE HAW HEEEEEEE HAWWWW" you screamed with the last shread of your human mind before it began to dissolve along with your body as it swelled to be the proper size of a beast like you and your hips violently snapped with a thrust from your new HUGE mate behind you. Your words made something in him snap even more as he grew larger and larger, his ribcage popping bigger and bigger with each strained breath, his back stretching more and more with each pump of his cock, and his hips finally snapping to release a pressure he didn't even know to be present.
With his body now fully that of a beast, he grabs you at the nape of the neck with his teeth and finally gets the perfect angle both of you craved. Your bodies swelling even bigger than before with pleasure as he screams out "OH FUCK I NEHEEE HAW THIS RIGHT FUCKING NAWWW HAWWW" in his last human words before releasing his hot donkey seed deep into you. You both cry out in brays as he clamps down hard with his teeth then once his cock slows to a weak drip inside of you he dismounts and walks on all fours for the first time.
You both breathe heavily but look eachother in the eyes with an odd newfound love and lightly nuzzle eachothers faces, giving a few kiss licks. You may both now be permanently huge asses but at least you are not alone.