Your girlfriend can't resist his body's attraction to you for a moment. His toned form is right in front of you in an instant, and as he kisses you passionately, you feel his rock-hard cock rub against your leg and a shiver runs through you. Everything about your girlfriend's new body is bigger and firmer than yours, and as you kiss him, your body starts responding in its changed way.
Your nipples become erect and your clit engorges as you feel his warm, intensely masculine presence against you. A strange warmth also emerges between your legs as your slit starts to moisten with female juices, a new aching need brewing in your crotch, a need to have him in you.
When you break the kiss and look at him, you realize he's feeling similar confusing but intensely pleasurable feelings. His large, firm hands cup your chest and a whimper escapes your lips, like he's squeaking a toy. Just to establish he doesn't have all the power, you feel his hips shake and his cock twitch. "Want to do something with this?" you ask, surprised at how sultry and high your voice is compared to how it was as a man.
"I wanna fuck you with it," he says bluntly, his fingers reaching to pinch your nipple. You moan approvingly, and spread your legs. A shiver races through you as his head rubs against your clit, emulating something you always like to do when you've had sex normally. It really makes it sink in how you've both changed: his body has become virile, handsome, and perfectly moulded to fuck people up and fill them with his seed; yours has been made nubile, beautiful, ideal to be played with and filled up and cummed inside.
He moves his shaft down and into your moistened vagina, and your heart almost stops at how weird and amazing it feels. His hands holding you up against the wall, he pushes all the way into you until his balls touch your crotch, and he remains still as a statue as your pussy slowly relaxes around him. Having your body filled like this feels so different to what you'd ever expected- you'd tried anal once or twice with guys, but you always had to lube up or it'd hurt. This just feels natural and perfect, and the weird thrill of someone you trust completely using more force and pleasure than is in your whole body to fuck you is incomparable.
Slowly he starts moving, and his rod pounding your body feels amazing. Unsurprisingly given you're both so unused to your bodies, pretty soon he reaches his first male orgasm and you your first female orgasm. He groans as your pussy clenches around him and cums inside you, and the feeling of his balls spasming against you and his cum painting your passage pushes you to your peak. Your insides cling to his cock and you feel your body shaking uncontrollably, his hands holding you tightly as you feel like you could just float away.
Once you've both finished cumming, he carries you to the bed with shaking hands and both of you collapse onto it, kissing each other weakly as he withdraws. You see his cock is coated in your juices and a few streaks of his semen.
Exhausted and satisfied, you drift off to sleep in each other's arms.