Isaac woke up the morning of the change feeling weird. He sat up in bed, and suddenly realized something felt off.
Looking down, he saw his blanket was held up weirdly high on him. Moving it off his chest, he gasped as he saw and felt his tits. Why so surprised? a part of him wondered confusedly. You've had them something like 6 years now, you should be used to them.
But he could tell something was off. He felt an odd dissonance with his old self, as if his existence as Isaac, and using that name, wasn't really who he was. He had to admit, the person he- she?- was now was pretty, or at least her tits were. Getting up, he wandered over to the mirror to see her body, and confirmed it- yeah, she was pretty. And so was he, he figured.
Suddenly, memories came flowing back to him from when he'd been, like, 12 or 13. He'd been one of the tallest boys, just as tall as the girls with their early growth spurts, but soon realized he wasn't growing like the other boys. He didn't develop hair or have his voice break like they did, and his package didn't seem to be getting bigger. He figured he must just be a late bloomer, until one day he realized his nipples had got larger and more sensitive. When he went to the doctor, they explained he had protoandry, a condition that causes boys to develop into women at puberty. Fortunately, after talking with the school and his family, Isabelle had managed to adjust to it properly, get a supportive friendship group, and most importantly, had safely developed from he to she. Her breasts grew healthily, she'd developed a feminine figure, and his cock had redeveloped to a clit while his scrotum reshaped into a vagina.
Now she was 19, and hadn't thought of herself as a boy for about 6 years. But Isaac wasn't sure what to make of it- he hadn't been a girl, and didn't think he wanted to be...