Katy got up from the bed and knelt to the floor. She watched as Sarah's eyes grew wide and she was very well aware of what was happening in her little sisters mind right now. Sarah's humanity was at the verge of being flushed away by the all-powerfull canine lust that the collar injected into her young body.
Katy knew of these instincts and desires because she had already succumbed to the collars thrall when Clara had pur it around her neck the first time back in college. Katy knew that there was no way of resisting the feral call the collar radiated. You could only succumb to it and revel in the pure lust it imbuned one with, even when not wearing it. Once touched, forever affected. After the first transformation you were no longer human... you'd become something very different...
Katy still had a hard time giving the collar to Sarah as she herself was more then eager to turn into a dog bitch again, but adding another willing member to the growing pack of cursed dogs was more urgent right now.
The collar was power. The collar was control. The collar was pure lust - Katy fingered her wet pussy with abandon while kneeling on the floor in front of the bed Sarah was just about to fall on.
Sarah was right in the middle of what Katy felt to be the bonding stage. The collar flooded her little sisters mind with it's raw arousal and her tiny human self tried to resist. It would not stand the barrage of pure canine instincts. It would fall and Sarah would emerge of it as a newborn bitch. She'd become more beautiful than she would ever have imagined.
Sarah had fallen to the bed some moments ago. Her naked body shivered and her fingers clawed at the bedsheets.
Katy got up from the floor slowly and smelt the air. Even in her human form her nose sense of smell had grown better tenfold. Sarah's scent was changing from that of an average teenage girl to that of a bitch in heat. Katy smiled. No one could resist the collar and Sarah's eagerness to try it only helped the transformation.
For a part of a heartbeat Katy was scared of what she had become. She had entered her parent's house as a human woman, touched but not controlled by the curse, but when she finally had succumed to the collar some minutes ago, everything inside of her had changed. Her personality wasn't what she remembered it to be. What if she was wrong? What if she had to rescue her sister from the collar's thrall rather then push her toward an existence of canine lust?
A surge of pure arousal devastated the last vestige of caring humanity Katy had and flooded her blood with canine instincts. Katy growled lusty, her teeth had grown sharp points.
She had forgotten everything she'd thought about only moments ago as the curse took her by force again and let her grap for the canine dildo that was lying on the floor in front of the bed Sarah was still lying and shivering on.
"Enjoy, little sister, I'll make you my bitch now..." Katy growled quietly.
Katy took Sarah's legs and slowly pushed them open so she had a clear view to her sisters' vagina. Her own fingertips had grown into sharp claws and she left some scratchmarks on Sarah's slender legs - but Katy didn't care. Everything that was of matter now was Sarah's transformation.
Sarah was breathing hard and her head was flailing from side to side, but Katy concentrated on her little sisters center of lust for the moment. She knew what she had to do and she would do it with pride. She'd turn her sister over to the canine side. She'd make her her bitch.
Slowly Katy touched Sarah's vaginas outer walls. The dark pubic hair of her sister felt good to the touch and the aroused scent that lingered around the wet tunnel only heightened Katy's own lust.
"Sister, pleeease..." Sarah moaned "do it, I beg you... I can feel the collar's call... make me... make me your bitch!"
Without further contemplation Katy opened Sarah's outer walls slightly with her clawed fingers and put the dildo's tip right at the wet tunnels entrace.
When Katy finally pushed the artificial canine member deep inside her sister's vagina, the collared girl growled in pure canine lust.
Katy started to push the dildo in and out of her sister and soon the lying girl met her sisters motions with demanding pushes and pulls of her own hips. Soon both girls were fully entranced in a game of pure arousal.
It wasn't long until the dildo triggered Sarah's physical transformation and opened her young body fully to the changing powers of the leather collar.
Katy could smell the oncomming transformation before it actually took place, because her sisters smell completely changed to that of a doggy bitch in the moment before the physical shapechange happend.
Dark fur blossomed everywhere on Sarah's body in an instant. Her muscles seemed to run like water beneath her darkening skin. Bone were reshaping themselfes. Fingernails turned into sharp claws. Leathery pads grew on Sarah's hands and feet.
Katy did not stop her wild dildoing until Sarah's body was changing so much that the girl had to turn around and get on her newly grown paws to allow her body to take the last few steps in reshaping her physical appereance to match that of a black lab bitch.
Sarah the bitch turned to meet Katy's gaze. She was panting hard and Katy could smell that her sister was in full heat right now, as all newly formed bitches were. She herself felt very sexually aroused at the moment.
So both of them had to get a hold on some nice doggy cock...