Ty watched in first horror and then fascination as the much smaller human woman standing in front of him suddenly staggered backward. The big black anthro horse grabbed her quickly and helped her steady with one hand, only to realize the meager amount of fat on her milfy body had suddenly melted down. She was now slim and shapely!
"W-What?" Mrs. Paulson looked over herself, eyes wide even as drizzles of horse jizz fell from her wet hair.
"Uh..." Ty gaped, realizing, watching as the woman was hit with another familiar jolt.
Sure enough, she gasped as her body tightened in seconds, gaining muscle definition and height very quickly, even as her hair color lightened and white fur began to sprout all over her body.
"T-Ty!" Mrs. Paulson cried, half in confusion, half in terror. "W-What's happening to me!?"
"You're... you're turning into a thing like me." He stared, breathlessly.
"O-Oh God!" She clenched her new muscle and let out a gasp as her pussy lips seemed to expand and moisten, her ass inflated, and her somewhat diminished tits regained their size and then some. Her ears grew to a point, her toes began to merge, and little by little she grew more and more equine, just like Ty had.
Finally, writhing, panting, gasping for breath, her rapid transformation was over. Still soaked in horse cum, the beautiful white anthro mare opened her beautiful blue eyes and shook her pure white mane as she stared at Ty in shock, raising her hands, looking down at her gorgeous snowy body, and noted her increased breasts and tighter stronger body. She didn't seem displeased.
"This is... gonna be really hard to explain to my husband." She snickered, whinnying. "Uh... god damn. I'm as big as you are now."
Ty couldn't fight the sight of the beautiful white mare in front of him. She smelt of his fluids, she smelt of a horny horse. She was gorgeous, female, and turned on. "Are you big enough to take my cock now?" He gulped.
Before he could even react, the tall and sexy white mare hammered her palm onto the big black anthro horse's chest and knocked him down onto his back. She kneeled down over his groin and started sucking his limp dick hanging from his sheath. It took only a little coaxing to get him hard again, at which point the athletic giant mare woman slammed both hands onto his chest, lifted her ass up, and dropped her sopping horse pussy onto his slick cock, still dripping jizz.
"FUCK! YES!" Mrs. Paulson-horse screamed in delight, and Ty grunted and dug his powerful hands into the floor as he received the first fuck of his life from a huge horny mare...
He reached up, grabbed her tits, and squeezed as she frantically drove him harder and harder, screaming and crying out as she got closer and closer to female orgasm.
And then... Ty relented. With a grunt, he spilled forth his seed into the horse woman, who cried out on top of him in orgasmic bliss. Still holding her tits, Ty watched as the mare cursed and cried out, grabbing the top of her head, eyes closed tight, and clenching his dick with powerful vaginal muscles, milking every last drop out of him.
As she sat on top of him, Ty realized very slowly, as delighted with pleasure as he was, that the beautiful white mare woman seemed... bigger. Indeed, little by little, lost in orgasmic stupor, the cum she had just received was making her grow and grow to bigger and bigger size. Soon enough, even sitting on him, her head hit the ceiling, and she surpassed even that, probably almost twice her former size as an anthro horse.
Her own orgasm subsiding ,Ty staring in abject terror, Mrs. Paulson fell to all fours with a thunderous slam and looked down at her man, eyes glassy.
"Oh! Oh my goodness!" She looked down uncomprehending. "Y-You've shrunken, Ty!"