It was early evening in a small suburb in Chicago. Two young adults, a boy and a girl, were walking down the sidewalk. The female of the two teenagers was named Alyssa. She stood at 5'7" and was 23 years old, and was laughing at a joke told by the other teen, Mark. Alyssa wore a black skirt that hugged her shapely hips and a light green t-shirt. Her hair was a short light brown, the same color as her eyes. Mark had been dating Alyssa for almost two years and he was 24. His hair was black and his eyes were a dark brown. He was wearing a white t-shirt and a pair of cargo shorts.

"Thanks for the wonderful time, honey." Alyssa leaned over and kissed her boyfriend. He was so nice to her and she'd had the time of her life on their date.

"Hey, I'm glad you did," Mark said, displaying a slight smirk toward Alyssa. He then gulped nervously as he stared at his date. "Hey, um, Alyssa?"

"Yes, Mark?" Alyssa asked, turning to her boyfriend. He was not usually this nervous. Something was up.

"Well, we've been dating for almost two years now, and I was wondering…” Mark looked around to make sure no one was around. He then slowly pulled out something from his pocket and showed it to Alyssa. It was a condom packet. "Think it’s about time we...did it?"

"Mark...that's...I'm speechless." Alyssa really was. She certainly wasn't a prude when it came to sex as she'd had sex with her previous boyfriends. With Mark, she'd vowed she would take her time before they had sex. "Mark, I..." She didn't want to be a cock-tease and have him feel like this would be a useless relationship. "You know what? Let's do it," she said.

Mark smiled and suddenly scooped up Alyssa in his arms. "Then what are we waiting for, babe?" He then preceded in running home with his best girl in his arms.

* * * * *

Later, inside Mark's bedroom, Mark sat Alyssa down on his bed. He immediately reached up her skirt and slowly pulled her pink panties down her legs and then threw them onto the floor, excited for what he was about to do with her.

"Ooooh," Alyssa blushed as she felt a slight breeze between her legs. Mark was certainly not shy about this. "Wow, you’re an eager beaver, aren't you?"

Mark began to sweat. "Oh, um...well, yeah...I mean, it is my first time, and I hope I'm not coming off as too forceful or anything."

"Well, take it from someone who's been there. I'm not going to run away in the next two minutes. Relax and enjoy yourself. This is sex, hun, it should feel good, not like it's something you have to do," she said, gazing into his eyes.

Mark sighed in relief. "Well...okay." He unzipped his pants and pulled out his shlong. "Let's try it without being naked first. Is that okay with you?"

"Alright Mark, we'll take it nice and slow," Alyssa said. "Now, tell me what you want."

Mark crawled onto the bed toward Alyssa, pulled her close, and slowly inserted his manhood into her womanhood. This new sensation he was feeling was fantastic. "Ahh...Mmm...This feels better than masturbating."

"Uhhh...Okay! That's it, baby. Give me everything ya got," Alyssa grunted as he filled her. She spread her legs as far as she could so he could go as deep as he wanted. "Yeah, nothing compares to the real thing," she giggled.

"Oh crap!" said Mark suddenly. "I forgot to put on the condom!"

"It's okay, honey. Just go with it." Alyssa tried to gently wrap her legs around Mark's hips.

Mark moved his hips back and forth, further pleasuring himself as his manhood slid around in Alyssa's pussy. He reached his hands up her tank top to caress her supple breasts as he continued to bump her.

Alyssa moaned as she ground against his hips. Oh, how she missed the feeling of sex, the heat, the passion, all of it was like some wonderful drug to her.

"Alyssa," said Mark hesitantly. "Hold on, I don't wanna cum in you."

Mark immediately took his manhood out of Alyssa and ran to the bathroom to ejaculate into the toilet. That was certainly a close one. If he had put on his condom before sex, he wouldn't have had to be worried about almost getting his girlfriend pregnant.

Alyssa laid there as Mark finished. She knew that as much as she would have liked him to keep going, he needed to pull out or she might end up pregnant.

Not a moment later, Mark came out of the bathroom and approached his lady on the bed. "Sorry about that,” he apologized. "I'm just not ready to be a father yet."

"I'm not ready to be a mom yet either," she said, leaning back contentedly. "Mark, there's something I need to tell you...about me." Alyssa was dreading needing to have this conversation.

Mark raised an eyebrow. "What is it, babe?" He sat on the side of the bed and caressed his girl's hips, looking rather concerned. "Is something wrong?"

"No...it's just that...well...I'm different from the other girls you have known," she said, trying to ease into the bombshell she was about to drop on him.

"Different? Like how?"

"Well...I'm a shape shifter."

Mark raised another eyebrow. "Eh?"

"A shape shifter...I can turn myself into any animal I want," she said, hoping this might help ease some confusion.

Mark couldn't believe what Alyssa was saying. Was she joking? Was she crazy? He didn't know. But, seeing as he had known her for so long, he just chuckled off the thought.

"I'm serious. I really can change shape!" She said, growing slightly angry at his disbelief.

Mark smiled patronizingly. "Alright...prove it."

"Okay then..." She got off the bed and looked at him. "Pick an animal, any animal, and I'll change into it right here in front of you."

"Any animal...hmm..." Mark chuckled to himself. He was sure Alyssa was playing a sexual game with him. Maybe she'd make animal moans or shed her clothes and walk around on all fours. This sounded fun to him. So, he decided to play along. "How about a horse...with a nice ass," he said, smiling skeptically.

"A horse...all right. You want me to keep my clothes on...or off?" She winked at him. Either way he would get what he asked for.

"Whatever you want."

Alyssa closed her eyes and focused. "Okay, one horse, coming up." She could already feel the change happening. She felt warm, but just let it pass over her as the toes on each of her feet began to merge together into hooves. So far it just looked as if her toes were webbed. Her ears began to shift up to the top of her head, forming points at each end and becoming light brown as this happened. Then the rest of the skin on her body began to change color from peach to light brown as well. Her toes merged into one large blob and morphed into shiny black hooves.

Mark's eyes widened as he couldn't believe what he was seeing before him. His girlfriend seemed to be mutating right before his eyes.

Alyssa just smiled as she couldn't help but chuckle at the goofy face her boyfriend was making. She knew he was freaking out, but she still thought it was somewhat funny. She turned away from Mark, showing off her back, then bent down, holding onto her ankles and exposing her round, supple, naked ass cheeks from underneath her black skirt. Her butt began to grow and became noticeably more muscular. And then a small boney nub began to emerge just above her butt and began to produce strand upon strand of long, dark, brown hair, which just kept growing longer and longer. The bony nub had become a flowing horse's tail. She grunted as she tried to remain calm through the change. Just underneath Alyssa's new tail both her anus and her vagina began to turn black and slowly swell up. Alyssa let go of her ankles and stood back up, her new tail lifting her skirt to reveal her now large, round equine rump.

She shoved out her chest which had become covered in the light brown fur under her shirt. The shirt seemed to grow as the breasts underneath it become more noticeable, her nipples tenting the fabric out an inch. There was no tearing, but still Mark could see her bust was more pronounced from the change. Alyssa turned to face Mark again as her neck then began to lengthen and thickened with a little more muscle, becoming more equine in appearance. Alyssa felt her face stretching and contorting to form a long snout. Her tongue became longer and thicker as her eyes moved to the sides of her head. Her appearance looked less human and more equine with every second. Eventually, her face stopped lengthening and she looked more like what she was; a busty anthropomorphic horse girl.

Mark took a step backward and immediately fell to the floor, staring in disbelief at the horse girl that stood in front of him. "A...A...Alyssa?" he asked in a nervous tone.

"Yeah hun, it's still me," she said, looking at the boy. "I told ya. Do you believe me now?" She sat down on the bed and looked at him. "So, let me guess... Now you hate me, and you think I'm a freak, right?"

Mark sat silently on the floor for at least a minute before he finally said, "How long...have you been a..."

"A shape-shifter. All my life. My dad taught me that I shouldn't advertise it to the world, as many people wouldn't understand what I am or think I'm some kind of freak."

"But...why do you change into...animals?"

"Well, lots of reasons...I'm angry, I'm scared...I'm horny. There really isn't any rhyme or reason to why I do what I do."

Mark got up from off of the ground and slowly approached his now equine girlfriend. When he got to her, he slowly put his hand on her hip and gently caressed it. "So...you can transform for sex?" he said, displaying a small grin.

"Well, yeah. And this form has lots of endurance." It was putting her mind at ease that she wasn't seen as some kind of monster by the man she loved, and that he wanted to explore this new secret she had told him about.

"Oh ,really?" Mark reached underneath Alyssa's shirt and began groping her left breast. "Mmm, think you can endure that?"

"Ooooh, I think I can." Alyssa leaned back, letting him groping her furred chest. The change had made her body much more sensitive and now it seemed as if he was picking up on her erogenous zones, starting with her chest.

Mark pulled her shirt up and began groping her breasts even more, even suckling at the tit.

Alyssa moaned in great pleasure as her boyfriend continued to grope both of her round, supple breasts, even letting out a small neigh as he continued. "Oh yes Mark....suck me," she neighed. She wrapped her hands around his head and held him close like a mother nursing her baby. "More!"

Mark stopped groping and sucking at Alyssa's tits, and stared deeply into her eyes. "How about you turn around, bend over, and put your hands on the bed? I got something in store for ya."

"Okay." Alyssa pulled away and bent over, her tail wagging back and forth in excitement before she tried to raise it as high as she could as she grabbed the covers of the bed. "Wanna put me through my paces?" she giggled.

"Oh, you don't know the half of it." Mark once again unzipped his pants and pulled out his manhood. He then pulled up Alyssa's skirt around her midsection, placed his left hand on her round rump, his right hand griping her tail, and slowly inserted his manhood into her equine anus, gently rocking back and forth from within.

Alyssa tried to say something, but it only came out in a soft neigh as her anus stretched to accommodate his length. She grunted slightly as she slowly moved backwards to take every inch of his manhood inside her. "Got more cushion for the pushin'," she giggled between soft thrusts. Never had she been taken this way by a guy but this was certainly a new experience for her.

Mark felt the sheer tightness of Alyssa's anus around his cock. It was both pleasurable and mildly painful at the same time. " Man...your asshole's so tight!" he said, as his pushing became more difficult.

“Well…ung! That’s one of the perks of…Ung…being a…ung…horse,” she said as Mark kept thrusting into her rump.

Just then, Mark felt a strong pleasurable sensation from inside his manhood. He knew what it was, and this time he was prepared. "Alyssa, I'm gonna cum!"

Alyssa looked around at Mark as he continued bumping against her ass. “Just let it go, Marky, baby!! Fill my equine ass with your seed!” she yelled, enjoying the feel of Mark’s manhood inside her anus.

Mark sighed in relief as spirt upon spurt of semen began to pour out from his cock and into the confines of Alyssa's anus until it began to seep out of the rim and drip down onto the floor.

Alyssa gave one final violent shove and she went rigid as her own orgasm hit her. The first hot splash of semen inside her anus made her quiver and she relaxed visibly as the successive rounds being fired not only filled her up but dripped out of her backside.

"Whoo!" Mark shouted. "That was...incredible. I've never felt anything this amazing in all my life." He then tugged at his willy, which was finally freed from the confines of Alyssa's equine anus. "How was it...for you?"

"Well, you certainly broke this little filly." She came back down off cloud nine and decided to stop the horse puns. "It was great, hun. You were an animal yourself. Maybe next I'll be the human and you can change." Alyssa lay there content at being so loved by this man.

Mark chuckled and then tugged at Alyssa's skirt, pulling it over her curvy hips and off her legs, tossing it onto the floor. "Alrighty, I already ejaculated. Shall we have a go at the who-ha again?"

"Sure, go ahead, lover," she patted her enlarged rump. "Gimme more for round two." Alyssa closed her eyes and got ready for him to enter her vagina.

Mark rolled Alyssa over on her back and inserted his schlong into her now equine vagina. As he pushed, he found that it was less constricting than her anus and smoother than her human vagina. "Ooh, this feels even better! Oh yeah!!" He took his left hand and groped Alyssa's right ass cheek, which felt like a balloon covered with a thick coating so it wouldn't pop. With his left hand, he lifted her shirt, exposing her breasts.

"Rub them, you know you want to," Alyssa neighed softly as she felt his phallus enter her. His hands were so good on her thick skin. Her sensitivity remained heightened by the change. Her breasts were so full and capped with dark nipples. "Yes!" came the sound from the horse girl as her boyfriend seemed determined to push every single sensitive button on her equine body. Mark's hand ghosted across her muscular butt cheek. "Don't smack it unless you wanna kick," she giggled.

"Oh god, Alyssa!" Mark said as he kept bumping Alyssa's vagina and caressing her round equine rump. "How could this get...any better?"

"Well, there is one way… You sure you want me to do it?" Alyssa knickered a bit as Mark started a hard in-and-out rhythm as he was fucking her.

"Sure…W-what is it?"

"We take this…all the way."

"You mean…have kids?"

Alyssa closed her eyes and concentrated. Her belly began to expand more, and soon it looked like she was pregnant, then grew to the the size of a melon. Her breasts began to recede into her furred body. Further and further they shrank, until they became absorbed by her fur. "Mark," she gasped as her ears detected the sound of something creaking. She would have said something but she had lost her ability to speak temporarily. She simply flailed about as Mark continued fucking her.

Mark's eyes widened in fear. "Oh god, what the hell?!" he said aloud, taking his hands off the still-transforming Alyssa.

Alyssa's shirt was torn to shreds as her chest grew more muscular, and her hands had now formed into fully-fledged horse hooves. Alyssa's hips however still seemed hungry for more of Mark's body as they pistoned harder and harder. Her hooves moved back and forth as if the horse girl was trying to stand up but, in what little remained human inside Alyssa's mind, she was trying to hold Mark closer to enjoy the wonder of the change. The creaking became louder as muscle after muscle was packed on with a vengeance and showed no sign of slowing. A loud crack was heard and then another.

Mark became scared at the creaking sound and immediately pulled his dick out of Alyssa's cooch. "Alyssa, Alyssa, stop!"

Alyssa only snorted as her anthro form took on more equine properties. Soon she had become a full blown horse, locked in the fury of sexual frenzy. The bed gave a final creak before Alyssa's full weight bore down on the helpless timbers, snapping them like toothpicks.

Mark stared in awe at the large horse that was once his girlfriend laying on the mattress that laid on what remained of the bed frame. He then pulled up his pants, zipped them back up, and slowly approached the large mare. "Alyssa," he said. "Are you still...you?"

"Yes Mark, I'm still me. I'm just a bit...bigger," the mare said as the once-human laid there, not trying to right her massive frame.

"You can still talk!!"

"Yes Mark...and I still want you. Don't be scared. I'm still me and you're still you."

"Uh...no offense, Alyssa, but maybe we've had enough sex for a while. Besides, making love to you while you look like that just seems...wrong. I'm really sorry, Alyssa."

"Well, ok, but I'm still in need... Can I at least have a kiss?" Alyssa's large head dropped.

Mark smiled, held Alyssa's head in his hands and planted a soft kiss on her lips.

"Thanks. Look...maybe next time I can be a different animal, maybe something like a cougar, or a wolf...maybe a little kitty cat?" she shook her head for a laugh.

"Sure, okay," Mark said, giving off a little chuckle. "Hey, maybe even a bird or a reptile, like a lizard or snake or something!"

"Sounds fine, so I'll go back to human and head home then." Alyssa said. She then closed her eyes and slowly transformed back into a naked human being right in front of Mark.

Mark stepped up to Alyssa and gave her a deep passionate kiss on the lips. "Good night, babe," he said, slapping her ass as she began picking up her clothes.

Alyssa yelped and just continued picking up her clothes, giggling sheepishly as she did so. When she was done, she put on all her clothes and left Mark’s room, leaving the poor boy wondering what to do with his now broken bed.