As Jon slept, his body began to change. First at the waist, and then running down the length of his lower body, his legs began to fuse together, the bone structures dissolving away as his spine extended out into the new appendage. Soon, his still-forming tail had reached the end of where his legs used to be and continued on, vertebrae and ribs forming all the way down, decreasing in size as they went.
By the time it had finished growing, Jon's tail was over fifteen feet long from his vestigial hips to the very tip, going from as big around as his torso at its base to somewhat larger than a bratwurst at the other end of things. As it finished its formation and growth, another change swept over his tail, covering it from base to tip in scales; creamy yellow-white for the bar-like ventral scales, and a rich emerald green everywhere else. The scales ran all the way up over his pelvis, with his genitals hidden behind a slit in a couple of the topmost ventral scales.
But the changes weren't over. The new snake-boy's hair lightened from brown to a rich gold color, growing out haphazardly until it reached roughly back-length. His normally square shoulders sloped and curved as his vestigial hips broadened, his entire framed softening and becoming less heavyset, though he'd never been that stocky in the first place. his face softened as well, becoming delicate and undeniably feminine as his skin changed from somewhat pallid and waxy to smooth and soft with a healthy tan.
As his arms and hands became slenderer and daintier, flesh began to gather underneath his nipples, erupting into a pair of full, rounded breasts that put somewhat of a strain on his ratty old pajama shirt. Finally, things rearranged underneath the ventral scales until the slit, along with the attached reproductive system, was all that was left; she was now in possession of all the equipment necessary for motherhood.
Jon the naga-girl rolled over onto her back, snoring softly, her tail gradually following suit.
Most kids were infected with the change virus by the time they were eight. Sometimes it was even earlier, if they spent a lot of time in close contact with other kids; children raised in a daycare environment were often exposed to it by five years of age. So for a twelve-year-old like Mikey, it was pretty much a given that he'd already undergone his infection, and had come through unscathed. And since the immune system was able to block it so effectively after the first exposure, that was pretty much all there was to it. Mikey wasn't going to change, and that was that.
Except that it wasn't. By whatever stroke of dubious luck, Mikey had actually managed to reach the age of twelve without ever coming down with the change virus, even despite a couple of exposures to infected kids. Today, however, Mikey had been exposed to Jon who had been exposed to Karyn who had been exposed to some kid in the hall at school...and he had managed to become infected through this exposure. Infection, of course, didn't neccessarily mean a change, but luck was not running with him tonight.
The first thing to change was Mikey's skin, which became a bright red, and took on a slight sheen as well. After this, his hair changed from black to a dark red, growing down to the base of his neck. Next, two dark bumps appeared, one on either side of his forehead, slowly pushing their way through the skin and growing into small horns. Two bony structures sprouted from his back, near his shoulder blades, growing in length and complexity, forming into leathery, bat-like wings, which folded neatly up against his back. His legs changed as well, restructuring into ungulograde form, his feet lengthening into a long segment that ended in cloven black hooves. His coccyx unfused and his spine began to grow out, growing into a long tail tipped with a cartilaginous, spade-shaped fin.
But, as with Jon, there was one final change in store for Mikey. Although nothing else about his pre-pubescent body changed to match it, his genitals shrank inside of him, forming into their female equivalents. Mikey would awake tomorrow as a young demon-girl.
