Derrick was walking home, his normal activity after school since he couldn't ever drive a car. And as usual he had a Gerald with him. The boy was the same age as Derrick, but all human. Not that he wanted to stay that way. If Derrick had been a Groom for the Centaurs, the human was a Groom for Derrick. He kept a brush and hoofpick handy, and was as attentive a servant as ever existed. Ever since Derrick had returned, the former classmate was now Derrick's tutor and valet and remembered being in this position since Middle School. Gerald was crazy about horses, the Clydes and Shires especially, and found the part-draft-horse Derrick to be ideal as a humanoid. Though he preferred the animals..
As the two headed for Derrick's house, Gerald sighed. "You are so perfect. Given a little magic, I bet you could turn me into a draft horse." Derrick cocked his head. "You love draft horses. Are you so sure you would want to be one?" Gerald nodded. "Impossible, I know. But if it were, man I would be first in line for hooves!" Derrick grinned. "I called a friend back at the Spa, and he sent me something I got in the mail yesterday. A brush that will turn a human into a drafter. Not a centaur, at least away from the Spa. A full animal. I can show you if you want. Maybe demonstrate it?"
Gerald stopped and stared. "You... I could be a horse for real?" This made the horse-boy chuckle. "Yes. But it would be total. You wouldn't exist as a human anymore. Once you were finished you would end up with a new equine life. Only I would remember that you were every human." Gerald was wide-eyed. "Please! Can we do it now? I want to be a horse! It's been a dream for years!" Derrick nodded and picked up his pace so that Gerald had to do a fast jog to keep up. "I figured you would say that - I have the brush in my stall out back."
Derrek had woken up one morning in a nice stall much like that at the Spa one morning, no longer having a bedroom in the house and not having used one since he was 7 or 8. Considering his frequent eliminations and ejaculations, the mess was a lot easier to clean up as mucking a stall than trying to get horse manure and cum out of carpet. He remembered being human and his past life, but everyone else only remembered Derreck as he was now.
They got to Derrick's house and went into the small barn that was Derrick's. He pulled out a carboard box and handed it to Gerald. "At the Spa it would make you a Groom like me, but here, it will only create a real horse." Gerald opened the box and stared at the plain wooden brush inside. Derrick continued "If you want me to use the brush, you have to remove your clothing and let me groom you. And once we start, you can't go back. I can make you part horse, or all horse, but any changes are permanent."
Gerald quickly removed his clothing and tossed everything into a corner. "I'll take anything I can get, but I really want to be a..."