...an Aztec. That sounded pretty cool, Ty thought. He had always thought Aztec culture was pretty cool, even if he didn't know a whole lot about it besides the parts everyone knew involving human sacrifice and being wiped out by colonizers. Having said that, he could just wish they would leave his people alone if they came during his lifetime.
He wished for his development to speed up until he reached the age he had been before he regressed to pre-conception, and for his perception and knowledge of his new life to catch up while he grew. Once he wished for it, some things shifted immediately- he saw his old self in his mind's eye as well as how he looked as a xygote, and his skin tone darkened to that of a native. Knowledge of the Nahuatl language of the Aztecs filled his head until it felt as natural to him as English, and so did an understanding of some customs of the tribe which he would live in.
After what felt like a few minutes, but naturally would have been 9 weeks, Ty's body reached the point of genital development, and something took him by surprise. He realized the sperm that had fertilized him did not have a Y chromosome like his original body, but an X. The point at which his labia and ovaries might have altered into a scrotum and testicles came and went, and their development did not abate.
Ty felt himself start to adapt to this with surprisingly little resistance. It felt natural given the altered nature of his conception- or rather her conception. He saw his nipples expand and breasts sprout on his soft chest. His figure slimmed down while his shoulders narrowed and his thighs widened. His penis shrank away to form her clitoris, his testicles pulled up inside her to reform into ovaries, and his scrotum split down its seam to form vaginal lips. He was now she, not male but female, not a young man but a young woman.
By the time she had finished processing her body's change in sex, she had been born and grown to her pubescent former age. She stood in a room she knew to be hers, and blushed at the realization that she was totally naked, covering her chest and crotch in case someone came in. She picked up some clothing from the floor, a bandeau and loincloth, and instinctively knew how to wear them. She tied the bandeau around her breasts and the loincloth around her waist and crotch. Part of her that was still used to being a boy from America still felt very naked wearing this, but she remembered that with the sweltering heat of the Aztec lands wearing more than this was rare- men often wore only a loincloth.
She also remembered what she was to do today...