Even if this naked little boy in front of you is technically just your girlfriend inside the high-tech bodysuit, it still feels so wrong that you want to make out with him/her. But still, he's your girlfriend after all, and also you're the one who turns her into a random boy you want to have sex. This is your kinky fantasy, so why don't you persuade him?
At that moment, you walk toward him/her and then you carry this naked little boy in the bed as he gasps and surprises at the same time, seems like this boy doesn't do anything but to let it happen. After you finally place him in your bed, your hands' cores hide his tiny body, so small and fragile. You easily pin the innocent little "boy" to the mattress, his slender arms unable to resist the strength of one of your hands while the other goes wherever you want. He can't stop you, and not that he wants you to stop. When your girlfriend turned into a cute little boy, he was confused at first when he didn't wear any clothes and looked at you as a stranger. Now you too strip off all of your clothes naked as you begin to have sex with him as you kiss him.
He moaned in seeming confused pleasure with your tongue thoroughly exploring his mouth. His hairless legs curled around your waist. A strand of saliva lingered as your lips parted from his panting mouth. His adorable face was flushed red and his eyes gazed half lidded up at you. Did he think you were done? Far from it.
Still pinning the little boy's arms above his head, you go to the nipple on his right nipple while your free hand plays with his left. To your surprise, your girlfriend/boy reacted far more to the nipple play than the tickling. Was he really that sensitive?
"Ah! Ah! Mister! Aaah! That feels...! Oh! Mmm... Oooh. No, please, slow down... I... I can't... Aah!" You do not slow down though. Nibbling, pinching, licking, flicking, circling, sucking... You play the moaning boy like an instrument until his quivering pleading becomes incomprehensible babble.
Sticking your fingers into his mouth and making him suckle on them, you use his saliva as lube as you begin to finger him, opening his hole one finger at a time. The poor boy doesn't seem to know how to process all these new experiences. Had you been more aware you might have questioned why you're sexually experienced girlfriend was acting as if she didn't even know what sex was, but right now you were just far too turned on to second-guess yourself.
Now he's finally ready. You let go of his pinned arms and use both hands to grip his hips. He's no longer trying to playfully fight you off him, but just twitching and drooling as if you've already broken his mind.
A twinge of awareness returns to his eyes as the tip of your lubed-up cock finds the naked little boy quivering hole. "Mister..." the boy whimpers, half in fear, half in need. You shove into him and he throws his head back and moans. One long passionate moan as you slowly push deeper and deeper and deeper into your transformed girlfriend.
Finally, all the way in, you look down at the gasping little boy beneath you. You can't believe how tiny his body is compared to yours. Yet you're inside him. Her? You don't care anymore. You just want to fuck. You need to fuck so bad! You pound away, holding the boy by the hips and thrusting as fast as you can. He cries out, clutching the bedding like a life raft. He's so tight as the bedrock as if on a turbulent sea.
You raise his hips so his knees are next to his head and you pound him directly down into the bed from above.
"M... Mister!" your girlfriend/boy cries out after ten minutes of relentless fucking. "Something's coming out...!" Sweat dripping from your chin, you pick up even more pace and time your orgasms to sink up. You fill the boy's ass as he lets out a stream of cum all over his face.
Panting, you lie down next to your girlfriend who is now a boy, and take some tissues from the box as you wipe and clean his cum covered face and body. After you're done, you then hold and cuddle him like you did with your girlfriend after sex, even though, this little boy is your girlfriend that you turned her into by the suit. "Umm... m... mister..." he breaks the silence and looks at you awkwardly. "I don't even know who you are, but when you and I did a thing, I felt like you and I were really close. Are you like, my brother or something?"
At that moment, you look at his cute innocent face as he's talking to you. You then respond to him. "Well, something like that. But you and I are more than that." You then kiss him lips to lips as he enjoys the kiss you give him. You could get used to your girlfriend looking like this. Or you could change him back to your girlfriend or even alter him.