Tom exited his car and waved to his girlfriend, Emily, standing outside of the stables. She smiled at him, waving back. "Hi, baby," she shouted. "How are you feeling?"
"A little nervous." His nervousness wasn't unwarranted, considering the adventure he was about to embark on. He would be letting Emily turn him into her horse. Just for the duration of the weekend, of course. Cleaning up the attic of the old house they recently bought, they had found an antique book. And inside, a transformation spell. It claimed to be able to alter reality, to not only change a person but change the world around them. To anyone not in the know about the change, it would be as if he had always been Emily's horse. Only the two of them would remember the old him. And once he was transformed back, no one would remember this alternate reality. It was clean and safer that way, he thought.
They'd planned the timing of the casting of the spell so that no one else would be around. Emily worked at the stables, as one of the horse trainers, so she knew the rhythm of the place. She'd taken on feeding duties this afternoon, and knew she'd be alone in this section.
She led him into an empty stall. Before she closed the gate, she gave him a kiss. "Are you ready?"
Tom swallowed, and nodded. "Go on." He could feel himself getting excited. His cock hardening. Ever since they'd started talking about it, he'd started fantasizing. Being a big strong stallion. He'd never been into animals like that, but with the idea planted in his mind, it had grown into something of a sexual fantasy. Emily had even promised him that if he was a good horse, he'd get to participate in a breeding.
Emily started chanting, reading the spell out loud. And Tom felt his body start to tingle. He watched in amazement as his arms elongated, his fingers fusing into hooves. "Do you accept this fate?" Emily asked in a serious tone. That the transformation was willing was a core part of the spell.
"I...I do," he replied. And then, the rest of the change hit him fast. He felt his spine crack, not painfully, but it forced him down on all fours. His arms - front legs, he corrected himself - were long enough to comfortably reach the ground already. His neck bent upwards, as his face stretched out. It was weird how his vision started to shift. A little confusing. His eyeballs being pushed out to the side. He could see behind him, almost all around himself, but only in front did his two fields of vision pair up into full depth vision.
His torso was stretching out, too. The clothes he was wearing seemed to melt into him, forming his fur. And there was a pressure at the base of his spine. His tail, growing out.
Suddenly, the scent of the stable hit him. His sense of smell had deepened. He could smell Emily from over here. There was a scent to her, a scent he recognized as...arousal. And he could smell the other horses living in here. The stalls were all empty, but he could somehow identify the scent of each individual horse.
The final change he noticed was between his legs. He'd expected his cock to grow, to become large and heavy, but... something felt off. He could feel his sex creeping upwards, back towards his rear. His ballsack sort of growing and stretching in a weird way, then split open as his cock slid into it.
"Me...mare?" He got the words out, strained, just before his vocal chords finished their transformation. He was all horse, now. She giggled.
"Yes, you're a mare, Tom. I mean, you never specified you wanted to be a *stallion*, did you? And besides, there are several stallions in the stables already. Too many tends to cause trouble, so my choice was between mare and gelding. And I figured you didn't want to be a gelding... So... you're a mare. A filly, to be exact."
That made sense to him...to her. She hadn't thought about that. Unsteadily, she walked over to her gate. And there, on a placard, she was. Tomfoolery, she could see. That was her name, apparently. Owner, Emily Swanson, sex, female, age 3 years. She was about to try to read more when Emily interrupted her. "What are you doing, Tomfoolery? I know we're alone in here, but I need you to get used to acting like the horse you are. And horses can't read.
*No, of course they can't,* Tom thought. And looking at the placard, the symbols no longer seemed to make sense to her. She pulled her head back up, stared at Emily. "Oh, just a side effect of the spell. It lets me help you along in acting like the mare that you are."
"So, what do you want to do now? Do you want to go for a ride, or would you rather head out into one of the pens and familiarize yourself with your new horse body?"