A guy?

...a guy. If that's okay..." you said as you're awkward and curious if she's could do that.

"You want me to turn into a man, hun?" your shapeshifting girlfriend asked as she's stopped moaning.

"Well,... yeah..." you answered and roll eyes awkwardly.

"Wait, are you bisexual?" she asked as she's curious about it.

"Y...yeah, I am but if you don't want to do it. It's fine, you don't need to do it and I don't **** you, babe." you answered as you don't want your girlfriend to get upset, exhausted, or disappointed. "So, we can just-"

"Nonono, it's okay, hun. I don't mind if you're going to say. Plus, I really like it." she replies.

"R...really, you really mean it?" you asked.

"Of course, I mean it, honey. Besides, I don't wanna disappointed my boyfriend, y'know. I just want to please and love my boyfriend, that's all." your shapeshifting girlfriend smiles at you as she makes you keep thrusting.

"Aww, babe. Like I just said, you don't have to do it for me, y'know. I also don't want you to get upset because I love my girlfriend and want to make her happy." you said.

"Me too, hun." she finishes and then kisses you passionately while you thrusting. "And you know, when you're saying that you want me to turn into a man, I wanna see the other side of the fence I'd love to be a guy."

With that, she pushes you back on the sofa as she climbs on top you and then kiss. During you both kiss, your shapeshifting girlfriend puts your cock into her asshole as you both have an anal sex. "The reason why I put it inside my butt, it's because I'm going to become a guy when I'm having sex with you." she explains as she continues thrusting up and down rhythmically. Without hesitation, she began changing right in front of your eyes while you both busy to make love. The first wave of changes erasing all her feminine features from her breasts shrinking till they left her flat-chested, her hips narrowing, hardening, and growing muscular to become unmistakably masculine. And as her vargina reform itself into her big penis, pushing outwards and paving the way for her testicles to emerge. "Holy shit!" You exclaimed and moan. "That was amazing…"

"I'm not done yet, hun. This is... just... a... beginning." your girlfriend replies as you can hear her voice is getting deeper.

And she was right, as the next wave of changes accelerated her masculinisation. The apparent surge of testosterone triggering the growth of a modest amount of body hair, mostly around her erect member, and armpits with a lesser amount covering her arms and legs. But the changes didn't stop at that, as you could clearly see her jawline gaining definition, and additionally, her hair shortening itself and restyled into a man’s haircut.

Finally, as she moaned in ecstasy, she coursed her hands over her new body, and as she did, her body gained a rather impressive muscular, suddenly you both couldn't take any longer and cum, her dick spread over your stomach as your girlfriend can feel how she cum as a man. When your shapeshifting girlfriend's transformation over, you pull your dick out of her butt as she (or more appropriately he) lays next to you and cubbles. "Well, what do you think about having sex with a man?" Ask the guy who formerly your shapeshifting girlfriend seductively with his new deep voice.

"Well, I'll say it's kinky that I would like to try something new, babe." you answer grab his/her thick ass and pull in to a kiss.

“So, what do you think we should do now, hun?” S/he asks, placing her/his big hand on your chest.