Eileen's shamelessly horny words, and staring at the handsome body of the dark young man above her, made Ty settle into her reversed role in sex. Now it was her turn to get fucked by a cock and bred like a bitch in heat, and the idea of getting filled with Eileen's seed turned her on a lot.
She felt Eileen's hard cock rub against her moist pussy, he thrust his hips forward, his shaft spread her lips aside and slid inside her- and he became a man, and she a woman. They gasped, practically collapsing onto each other in amazement at the sensations their new bodies were giving them, and hearing each other pant into their partner's ear only turned them on more.
Slowly Eileen got his hands either side of Ty and propped himself up, both of them taking the opportunity to gaze at the body of the lover they were inside and had inside them. Ty felt transfixed by Eileen's toned, trim figure, and Eileen by Ty's soft curves and pert breasts. More than that, though, they felt transfixed by knowing what was to come of this- Eileen was anticipating getting to cum inside Ty and make her pregnant with his seed, while Ty ached to have Eileen's cock inseminate her and give her a baby.
"Tell me when I can move," Eileen breathed.
"You can move now!" Ty almost laughed, and her laugh turned to a satisfied moan as Eileen pulled his hips back and thrust inside her firmly, filling her and rubbing against her G spot deep inside her. Further thrusts followed, eager and passionate with the overwhelming desire of youthful fertility, and Ty moaned louder and more keenly with each one.
Perhaps unsurprisingly, before long the two were reaching their peaks, unused to the pleasure of their new bodies. Ty's pussy began clenching tightly around Eileen's cock as it thrust in and out of her, and Eileen felt the motion of his hips seem to pass out of his conscious control and become governed by his instincts.
Their first orgasms in their new sexes came almost simultaneously. Ty felt her mind go blank and moaned erratically as her slit clenched around Eileen's cock in a way that seemed in time to the beat of her heart, and Eileen let out grunts and gasps of satisfaction as his balls pulsed against Ty's skin and thick strings of his semen were shot inside her.
Eileen collapsed onto Ty once again and, between pants, whispered to her to tantalize her further. "Now my seed is inside you, you're sure to get bred," he said. "I bet our child is forming already."
Sure enough, the ovum inside Ty was soon surrounded by Eileen's hungry seed, and they eagerly ate away at its walls until one sperm pushed through to the core of the egg and fertilized it.