Jim appeared in his bedroom. He knew this was the first place he would have to secure. He extended his senses and found hist stepmother in the back yard pool with his older stepsister. Judy was a 38 year old health nut. She had married Jim's father six years ago and had against all of Jim's expectations, been a good mother. Her two daughters, Cathy and Bobbi were likable enough. Cathy was 20 and attended the local college, while Bobbi was Jim's age. Jim smiled as he located Bobbi. She was in her room, mastrubating. Walking down the second floor hall, Jim approached her door. The loud music she was playing covered up not only her faint sighs and moans but also the sound of her door unlocking.
Jim crept into the room silently. Bobbi's panties were around her knees, her right hand under her skirt. Her left hand alternated between teasing her small breasts under her shirt and pushing her light brown hair out of her face. Her face was twisted in effort and her breathing had reached a pace that Jim knew she was on the edge of an orgasm. Bobbi's eyes opened slightly as she reached the cusp, flying wide as she realized she was not alone. With Jim's help, the shock of discovery pushed her over the edge, and Bobbi didn't even have time to speak before she was lost in a wave of pleasure greater than any she had experienced. She heard a voice moaning in ecstasy and almost came again when she realized it was her own. As the sensations subsided, she remembered Jim. Thowing her bedspread over her lower body, she was about to start screaming at him when she noticed his body.
Jim had always been somewhat soft, not so much as to be called fat, but he always had looked like someone who never did much activity. Something had changed, and even through his shirt, Bobbi could see that he was well toned and muscled for their age. She suddenly felt a deep shame for letting him see her like this. All thoughts about berating him for sneaking into her room vanished, and the only thing she could say was, "are you going to tell Mom?"
Jim smiled at Bobbi. She was looking at the floor, biting her lower lip. He wallowed in her shame briefly before approaching her. He gently stroked her arm, sending and electric shiver through her body. He leaned close to her ear and whispered, "not if I stand to get in as much trouble as you do." His nibbled gently on her ear, eliciting a shocked gasp. His hand slid under the bedspread and began massaging her mound. Bobbi moaned as he slipped his finger into her. She knew she should be revolted by the thought of doing this with her stepbrother, but deep down, she knew this had always been one of her fantasies. The orgasm hit her quickly and powerfully. As she clenched down on Jim's finger, he began thrusting even more fervently, keeping her cumming for almost a minute. Finally, she slid off the bed, and collapsed onto her knees on the floor. Dark desires swirled in Bobbi's mind. She knew that she would never have so perfect a chance to live out one of her sexual fantasies. Looking back at Jim, got onto all fours. The reaching back with one hand, she spread her sex and looked at him with pleading eyes.
Bobbi came again as Jim pressed into her. As he thrust, he wove his dark powers around her body. The hair covering her slit grew softer and straight, slowly creeping up her stomach and ass. She looked back at Jim lustfully, licking black lips with her long flat tongue. Her face was pushing forward slightly, stretching her jaws and nose. He heard a slight wimper as her shoes began to swell, and as her lengthening feet started tearing through her leather sneakers, Bobbi yelped in surprise. She looked back at her body, her yellow eyes wide with fear. Brown fur covered her ass and upper thighs. Her clawed feet had torn through her shoes and were now being covered with the same fur. Jim couldn't hold back any more. Bobbi had been dreaming of a perfect sexual encounter, and the fear and horror of what was actually happening to her pushed Jim into his own orgasm.
As Jim came inside of Bobbi, she could feel the changes accelerate. Her chest began to swell, straining her shirt. Bobbi howled as she came, her face no longer human. Her fur crept over her growing chest and spread down her arms. Thoughts and desires began to infiltrate her mind. She tried to resist, but as she felt her fur creep up and over her face, the throughts insinuated themselves inside her. She belonged to Jim, and it was her duty to protect him. The young werewolf howled again in pleasure as she prepared to serve her master.