Deciding to push the limits of what he could do to humanity, he opened the book to the section on humans and began to re-write it, starting with erasing the title "human" and replacing it with "dragon".
Quickly following up he rewrote the gender ratio section to 100% female and can reproduce without a need for a sexual partner so long as they orgasm to trigger ovulation.
The rest was fairly straight forward, writing that instead of arms they had forelegs that could function like hands, that they were quadrupedal, that they came in many unnatural colours, their magical wings able to carry them despite being only medium sized, their scales, their tail, and claws, their various breath weapons, and their long lifespans that last for hundreds of thousands of years...
… All the while he felt the changes slowly sliding up his body as he wrote. He got to the section on the former human's mammalian breasts however and decided to let it stay unaltered. He also left the hair, butt, and vagina from humans the same, and the book seeming to read his intent left it alone; perhaps since he seem to have insisted on re-writing the human section himself rather than leave it to the book.
He put the book away where nobody would notice, and focused on his own changes, most of his body was already covered in red scales, with light blue on his underside, and his manhood was finishing its shrivelling into the opening slit that was left in its place. With him now a her technically, her young breasts began to puff out a little, but she found herself a little disappointed when they were barely halfway between an A cup and a B cup; realizing that with her having been only just starting puberty when she was a human male she'd have to wait for them to grow in... Perhaps a few thousand years if a single dragon year was a thousand human years.
The line of thought distracted him from her changes until her new wings burst out of her back. Remembering her changes, she looked around for a mirror, noticing her dresser mirror quick enough to see her muzzle finish forming as a pair of cute little horns poked out of the back of her blue hair, her pink slitted eyes providing a nice accent to her red and blue colour scheme.
She found herself quite attractive, her tail wagging behind her as her new sex dripped. She found herself thinking she could very well just mate with herself now, bare her own eggs and become gravid and pregnant. She held back though, figuring it would be best to see what had become of the rest of the world before she indulged in her own sexual fantasies
She opened her drawers and started re-dressing herself, finding it amusing how difficult it was to stick her wings through the new holes in the back of the shirts she had; said shirts looking much the same style as they did before, but better hugging her form, especially her breasts. In fact most of her clothes were the same as before but tighter, that her pants had a tail hole, and her shoes only had soles on the ball of the foot with holes for her claws, while a new pair of gloves matching the shoes being placed alongside them. She was amused to find that her underwear was boyshorts instead of panties, and her matching bras looked like sports bras but less constrictive.
Realizing she was suddenly looking through a girl's underwear, her own underwear, she found one of her claws slipping into her own dripping pussy, only to chide herself that she still had other things to do. She ignored the bra considering she barely had much for breasts and left her shirt on, slipping on her boyshorts and a pair of loose running pants. Opening an extra draw that wasn't there before, she suddenly blushed as she saw what was inside.
Unlike her own personal wear, the drawer was full of skirts and button up shirts. It was practically a Japanese school girl uniform, which considering she actually was still in school, and she was a girl now, is exactly what it must have been.
She handled a pair of pure white stockings, it looking like it would go all the way up to her thigh, and she couldn't help but wiggle her ass as she tried to restrain her embarrassed arousal at the idea she might have to wear them. Like her shoes, they also had holes for her claws, and came with a matching pair of sleeve gloves that would go up to her shoulders. With a bit of apprehension, she closed the drawer and sighed.
She soon wondered what her name would be now, considering "Ken" might not fit as a girl's name, or maybe it would if there's only one gender for dragons.
Shaking her head, she decided it was more important to think about if she wanted to get to know how her family had changed first, or if she wanted to go out and see how her friends had changed.