Allan was a 20 year old guy, he wasn't successful with girls and that was no surprise to him. He was really fat, apart from the pile of pimples on his face and his crooked teeth with braces. Because of this he had become very introverted and spent as much time as possible at home, only going out when he couldn't help it. The time alone helped him develop a desire, for which he bought a microcamera over the internet. He knew one of his neighbors, a very hot woman named Kadence, lived alone.
He waited until one night when she was gone and all the other neighbors were asleep, then he went to Kadence's house, unlocked the door using paper clips, and went inside. Finding her room, Allan hid the microcamera configured to send real-time images to his computer and returned home.
Only at the end of the next day did Kadence return home and Allan watched from his house as she entered her room and began to take off her clothes. As he watched he stroked his hard cock and became more aroused when she took off her underwear as well, sat on the edge of her bed and began to masturbate.
What happened next was something Allan wasn't prepared for, out of nowhere Kadence's eyes gave off a red glow, quickly she grew to be two feet tall, her breasts doubled in size, her skin turned completely red, a pair of horns grew from her head, her feet became hooves, a tail grew behind her and her pussy inverted into a huge ballsack as her clit expanded into a two-foot equine cock. He couldn't believe he had just found out that the hottest woman on the street was a demon.
Allan thought about using this discovery to blackmail her, but then she looked straight at Kadence looked straight into the camera, continuing to jerk off with an evil grin on her face. She got up from her bed and pointed her dick at the camera, making Allan wonder if she had noticed the camera there.
When Kadence came, Allan was surprised that instead of just hitting the camera, the demon's cum went right through his monitor screen and hit him full on.
"Did you like it Allan? You saw me as I really am, you already know my biggest secret. Now, you messed with a demon and you're going to pay for it." Kadence said, demonstrating that she knew all along about the camera and that he had installed it there.
Allan tried to run away as fast as he could, but his bedroom door had been magically locked by the demon and he couldn't open it at all. He pulled the doorknob with all his strength, throwing all his weight trying to force the door open, but the doorknob broke and he fell, hitting his head on the edge of the table and losing consciousness.
When Allan woke up, he didn't know how long he had been unconscious, he just knew it was night. He noticed a steady thumping between his legs and looked up, being surprised to find that he was naked and being fucked by Kadence in her bedroom. Another big shock was discovering the size of the change in his body, which was definitely not a 'he' anymore, Allan's body was now a girl's and already had Kadence's equine cock going in and out of her pussy.
"Finally you woke up. Do you like your new body?" Kadence said
"What did you do to me?" Allan asked
"It's your payment. You wanted to see my intimate and your wish was granted, but you messed with a demon and there's a price to pay for that. Your payment is to serve the rest of eternity as my slave. You will have the rest of your life living with me in your new identity, which to others is my sister Anna. After your death you will be turned into an imp to continue to serve me." Kadence said
"No, you cannot do that. My family and friends will look for me and when they find out what happened you will pay." Anna said
"Fool. No one will find you. Allan will remain missing until he is presumed dead, for he is no more, and you will never be able to tell of our true relationship or reveal my secret to anyone. If you try to do so, you will have a coughing fit that will make it impossible for you to say anything." Kadence said and thrust her cock a few more times hard into her slave before cumming inside her.