When you went back to the point that you went back in time you saw Cathy as a centaur trotting around and you noticed that Sara came up to her and you looked in shock that she was also a Centaur.
Sara trotted up to you and said 'Hello cous.'
She flicked her tail in excitement, I could tell she was in the heat. I made the wish that I could become a centaur and fuck her. As soon as the thought had finished I immediately stripped naked. I noticed that chestnut brown fur was growing all over my lower body, my dick was growing an equine sheath and my balls inflated. Sara couldn't help but stare, excited by the proposition that I was offering. My feet had darkened and shrunk becoming hooves right as my spine extended and a tail grew.
Soon the transformation was complete and I mounted Sara. I fucked her animalistically ensuring she would screw in lust as I came into her multiple times. I then smacked her ass and chased after her as she ran away satisfied with what I had done to her.