Kelly, not realising that someone was home, yanked her pants down under her dress and just started fingering herself in the middle of the kitchen. Her other hand found its way to her breasts, pulled them out of the dress and started playing with her nipples. Her tail, seemingly of its own accord, wrapped itself around Kelly's waste and started to brush itself against her clit.
"Mooooo" escaped Kelly's lips, rather loudly as if she was surprised her tail was capable of helping out. She couldn't help making noise, and had completely forgotten about the car in the drive, or Emily's chat, when she turned and saw Marcus stood in the doorway.
Her eyes immediately darted down to the bulge in his pants that he had quite obviously been rubbing while he watched her. Part of Kelly didn't want to fuck her sister's boyfriend, but the other part of her that seemed to now be her Bovine desires had already approached him and started making out with him, yanked down his jeans and began jerking his cock. All Kelly needed right now was his cum inside her. She needed to breed.
Kelly walked away from Marcus and bent herself over one of the counters. "Please fuck me I need it". He didn't need asking twice, and walked over and fully entered her in one push. At first he thought it was weirdly spacious inside her, but then the walls of her pussy started expertly working themselves to get what it needed.
Kelly was in ecstasy again, this was exactly what she needed. The weird feeling returned, this time on her head. As Marcus started fucking her harder, her ears started to change shape, and move position on her head. More Moos were escaping Kelly's mouth. She couldn't help it, they just happened when she felt so good. Within a few minutes it felt like Marcus was ready the blow, and Kelly started to feel him pull out.
"Moo!" Her hands moved towards him and pulled him back into her, just in time for him to start pumping his sweet seed inside her.
Kelly came with him, causing her ears to fully change into floppy little black and white cows ears on the side of her head. But the feeling hadn't gone away yet, there was still a sensation on her forehead, and she wasn't letting Marcus go until it was done. At this moment in time she needed these changes, she NEEDED to become more like a cow.
Marcus pulled out, as if he was done, but Kelly grabbed him and pushed him into a dining chair, and impaled herself back on his cock before it could start to shrink down. She rode him with every fiber of her being. She needed more cum and she needed it as fast as he could give it to her. Bouncing up and down in his lap, the jiggling of her new tits was making them leak a little. Without thinking, she shoved a nipple into Marcus's mouth, and he just automatically drank from it. After tasting a little bit, Marcus started to drink more heavily from it. It was good. It made him feel good.
Kelly was already in her own little orgasmic world when he started drinking from her, but it felt like he was also growing inside her. She resigned to think about it later, as she felt his larger cock getting ready to blow. She stopped her bouncing and pushed herself down on it as far as she could go. It didn't concern her that she was taking the whole thing, as it started pumping more cum than the first time into her.
Kelly's forehead burned up as she came again, small horns pushing their way through the skin.
Marcus looked like he was ready to pass out and wasn't really paying attention. But even if he was, who would believe him anyway?
Kelly returned somewhat to her senses and eyed up the mess she'd made. It probably wasn't going to be long before Emily got home so she needed to tidy this up. Kelly pulled her pants back in under her dress, and noticed they felt a little tighter around her hips.
"Marcus, this never happened okay?" She demanded.
"Sure" he said, coming back to his senses. "I won't tell anyone about any of this, but on one condition. We get to do this again"
Kelly wanted to say No. No she wasn't going to be the 'other girl' of her sister's boyfriend. But her lips had already smirked and agreed.
Marcus helped Kelly clean up the kitchen and then he returned to Emily's room. Kelly went to her own room shortly before hearing Emily get back, not wanting her to see how she's changed.
Kelly stood in front of the mirror completely nmin, examining the changes to her body. She actually thought she looked pretty cute with the horns, ears and tail. Her curvaceous new body was definitely sexier too. Her breasts were bigger, her hips had widened slightly, creating a slightly bigger ass, and wider thighs. In fact she felt slightly bigger over all. Definitely not as slim as she was this morning.
But she was concerned about her mind. Her normal regular thinking was still intact, but the more she indulged her new cow desires, the more control it had over her actions. In half a day it had already made her eat grass, drink 2 pints of milk, and fuck her sister's boyfriend, twice. At this rate she'd turn into a complete cow within the next few days. But for some reason that conclusion didn't panic her, it actually felt kind of reassuring...
Her mind started wandering again, her desires leading them. Maybe being a cow wouldn't be so bad. A little bit of grass right moo sounds like a good idea, or another glass of milk. But she also felt like she needed more cum inside, and Marcus was too occupied now to help her with that. And what about the farm she wanted to check out too.
Kelly needed to decide what she wanted next.