The two pressed against each other, groping wildly as they passionately kissed, Chad tried to tell Diane that they shouldn't, as Diane tried to tell him the same thing, but neither seemed to be able to control themselves. Both starting to double in size, Chad eventually managed to push Diane away, but only so that he could grasp her penis, which had tripled in size and had developed a sheath, and slowly bring his hand up and down the erect shaft.
A moan of pleasure erupting from Diane, she whispered, "We need, we need," tried to say that they had to stop, but instead moaned again and instead finished her sentence by exclaiming, "We need to put it in you."
Disturbed by how turned on, Chad wanted to step away. Instead, he nickered in excitement and whinnied, "I want it in me," as thoughts about being lain down, spreading his legs and allowing Diane to penetrate him raced through his mind and a slick feeling developed between his legs.
To his surprise, Diane neighed really loudly and shrilly as she abruptly spun him around. Alarmed, unsure what it was that she was about to do, Chad found himself bending over and presenting himself. Rising up onto the balls of his feet, he whinnied again and as Diane began rubbing the tip of her penis against his vulva, Chad missed it completely as his toes turned black, his feet morphed and a hard hoof began to form. Behind him, a pressure starting to build in her testicles, which felt heavier, Diane also rose up on the balls of her toes and thrusting forward, she penetrated Chad as she lay across his back, her increasing weight causing him to drop to all fours and brace himself.
His mind practically screaming everything was wrong, that he shouldn't have the girl parts he had, that it shouldn't feel good, or be even possible, for him to have a penis that was over two feet long shoved into him, Chad nickered in alarm and shifted in place. Thinking he was doing so in attempt to pull away, he found himself terrified to learn that it was actually in to better position himself. Hearing a cracking noise coming from both him and Diane, he wondered how it was that his girlfriend weighed so much and that he was able to still remain standing with her lying across his back. Missing completely that both him and her had been reduced to a quadruped stance, Chad slitted his eyes shut in enjoyment and tried to extended his neck out as far as it would go, which in turn caused it to start to lengthen.
Behind and on top of him, Diane had lost herself to the need to satisfy and fulfill the lust that had swept over her. Oblivious to the fact that she could no longer stand on two legs, she watched as her hands began to morph. Wanting to stop as she realised what was happening, she found she couldn't as a bestial nature came over her and trying to scream in terror as she found herself looking at what appeared to be the back of a horse's head and neck, Diane only managed to neigh in pleasure. A sound that was answered by the animal that was below her. Understanding briefly coming to her that the mare she was fucking had been been at some point her boyfriend, Diane watched the female horse toss her head, shaking her chestnut mane in the process, and reveal a hand that was still pushing outward into a horse's muzzle. Trying to scream out, but only neighing, Diane thought, "Oh shit. What have I done? What is happening to me? What is happening to us?" before she felt herself let loose into the mare that had once upon a time been her boyfriend, the human side of her thoughts slowly drifting away as she, now he, did so.
From beneath her, Chad found that he was for some reason still able to retain his human mind as he tried to fight against the animal that was threatening to over take him. Feeling the stallion shoot his wad into her, Chad whinnied in delight and immediately thought, "No. No. No. I am not a horse. I am a human. I am a," but losing her train of thought, she found herself shifting in place as the stallion pulled away. Glancing back behind him, seeing a huge, and beautiful, black horse that had what hair around the hooves, Chad ruminated, "What is my dad going to say when he comes over and finds two horses in the living room?"
No answering coming to him, Chad looked away, scared that she might more get turned on, and instead focused on finding a solution to their problem. The last bits of their transformation, a tail and ears, happening, Chad nickered softly and tried to sort out how it was possible for two humans to be turned into horses. Latching onto the concept that she wasn't a horse, but a human, Chad stamped her hoof in agitation when Diane nuzzled his flanking. Glancing at the other horse, she started to tell him to knock it off and help her think, but didn't bother as she decided the only sounds she could make were normal horse sounds, as well as seeing in Diane's eyes there was no humanity left.
Upset by this, believing it would likely be his fate, Chad neighed in alarm and stamped her hooves. Thinking, "I don't want to be a horse. I don't want to be a mare. I'm supposed to be me, Chad. Sixteen-years-old. Human. Not Chad the however old horse," she watched, and felt, as Diane again nuzzled his head against her before apparently losing interest and wandering off. Wanting to prove she wasn't a horse, Chad thought of things she could do that a horse couldn't and settling on walking on two legs, she decided to settle on first trying to reacquire that ability.
At a loss on how he would, Chad thought for a moment, her tail flicking slowly back and forth as her ears swivelled, listened for any sign of danger. An idea coming to her, she started to think it wouldn't work. But, not wanting to focus on the negative, Chad tried to sort out how to carry out his plan. Spotting the nearby wall, she thought it would help and trotting over, she took a deep breath, preparing herself. From somewhere behind her, she could hear Diane getting into something and telling herself, "Deal with it later. First, try and regain your humanity," Chad took another calming breath and feeling she was ready, she tried to force herself up and onto her back hooves, telling herself, "You're a human. You walk on two legs. You speak English. You wear clothes. You live in a house and go to school. You are a sixteen-year-old human," as she did so.