Diane pulled herself upwards, keeping their bodies together at their crotches but otherwise trying to get a better look at Alex's transforming body. His own gaze was drawn to her handsome face, masculine figure and toned muscles, to say nothing of the huge thick cock rubbing his own.
Suddenly, he felt Diane's shaft slip off his own, and press against his scrotum. To his surprise, he felt it push his balls inward and panted as they slid inside his body without resistance. His emptied nutsack seemed to pull inwards until the skin was almost flush with his crotch.
But the feelings Diane had mentioned were really kicking in for him now. His body was producing feminine pheromones at an amazing rate, and it was getting both him and Diane so fucking horny. He felt a weird twinge run through his chest, and then looked down to see his nipples swelling and enlarging.
Diane's hands moved to his chest, and she purred, "mind if I...?"
Alex nodded, and when she cupped the slowly accumulating flesh and rubbed and pinched the nipples, they both watched as mounds of soft flesh grew under her hands. At one point she bent down to suck on one of them, and Alex let out an unbridled moan at how weird and pleasurable it felt.
Pulling back again, Diane started playing with them with her firm hands, sending intense pleasure through Alex's body and reinforcing to him that these were his breasts, what remained of his masculinity rapidly fading. By now the feeling of hardness in his dramatically shrunken cock was accompanied by another feeling. A feeling of... emptiness. Having Diane's huge hard cock against his own tiny, sensitive one made him ache to have it inside him.
A moment later, another thrust from Diane made Alex's penis finally shrink to a tiny clitoral nub, and her cock slipped upwards and pressed against his stomach. When her balls touched his flat crotch, it finally opened out into a moist vagina, and the view Alex had- of a handsome man between his legs with her cock straddling his moist pussy- turned him on so bad.
Diane smirked and regained her composure, positioning her cock head against Alex's waiting slit. She looked down at it in amazement, and breathed, "whoa, it looks so juicy." Alex moaned, feeling her shaft throb against his opening, imagining how nice it'd feel inside him.
"Please, can I fuck your pussy?" she asked.
"Of course," Alex breathed. Diane's hips thrusted into him, and he clung to the sheets and whimpered as the thick shaft filled him up. He felt every vein of that large, thick shaft filling him up, his body clinging to it as Diane slowly started to thrust.
The two of them were being overwhelmed by the intense transformed mating instincts of their new bodies. Diane had had any feminine desire to carry young wiped from her and replaced with virile lust, so she now ached to fill Alex's womb with her cum and impregnate him. Likewise, Alex's masculine urge to inseminate others had vanished now he'd been emasculated, and he now felt nubile instincts instead, desperate for Diane's thick cock to fertilize him.
Her penis pounded his vagina tirelessly, her balls slapping against his crotch with every thrust and her head repeatedly brushing against his G-spot. Every moment of their fucking reminded her how she had become a man and him how he had become a woman, and it felt so good.
At last Alex heard Diane grunt and felt her twitch, her cock shooting a huge load of cum inside him. They looked at each other breathless with pleasure, and kissed passionately, the afterglow of having cum inside someone and been cum inside filling them.