Aaron considered this for a second, and then said, "Yeah, I guess I do. I don't want anyone to see me as a boy."
"In that case," the voice asked, "what would you think of me changing existence so that you were born female?"
"You can do that?" Aaron replied, amazed.
"I can, and I will," the voice answered. "I hope you're ready to be made a woman, Ariana."
The young man was amazed how he heard that name and felt a connection to it. All of a sudden, he found himself sitting and leaning on nothing, as the void's chair and table vanished- and a second later his body vanished.
He saw a vision of inside a vagina during sex, as a penis thrust in and out hard and fast. It sped up more and more until it began to ejaculate, and the perspective moved to show the sperm that swam inside the semen, seeking an egg to fertilize.
They soon came upon the egg, and one pushed inside to fertilize it... only for time to spool back and a different sperm beat it to the punch. "Now your conception has been altered," the voice said, "you will be female instead of male."
Aaron could see his body again as well as the fertilized egg now, and while he saw it settle into his mother's womb and develop in a sped-up vision of the process, he felt the change's effects ripple through to him.
A tingling spread through his face as its features altered- his neck narrowed and his larynx shrank, giving him a higher-pitched voice; his jawline softened and his lips turned puffier; and his hair lengthened partway down his back.
The changes spread further down his body, his skin smoothing as most of his body hair vanished and his muscles turned more petite and lithe. Even his memories of his life seemed to be altering, as he saw different people as friends and recalled being known as 'Ariana' in this life.
Soon the changes he most closely associated with becoming Ariana took hold. His chest grew sensitive and his nipples expanded, before breast tissue began sprouting around them. At the same time, he saw his hard penis start to shrink away inside him. His testicles were tugged into his body and reshaped into ovaries. His scrotum seemed to invert as it began to turn from a sac to a slit.
This whole transformation was castrating and emasculating him. A boy or man would find it awful- but she wasn't a boy or a man, she realized. As her penis reached its tiny new size as her clitoris, her womb formed inside her and her scrotum spread open into vaginal lips, she felt herself acknowledge she was a girl.