A simple premise.
You live in a world where males are born meek, small, thin, with small… endowments. To be honest, if males didn’t end up with intelligence and cute, shota looks, they would be rather worthless to keep around.
On the other hand, females are different. Breasts, tall, and both reproductive systems incredibly common. Women are naturally both gorgeous, and well-endowed, with breasts larger than their own heads, penises that can go to their mouth when erect (this is including the fact that most are well beyond six feet proportionally, sometimes seven feet on the taller side), and abs that look like they could kill.
You are a young boy in the midst of high school. The meekest of even the meek males. Often bullied and made fun of for being tiny for the tiny gender. So it definitely came in as a surprise when you were selected for a special study to transform men into women.
“Doctor, will this shot really make me into a female?” You ask, looking up sky high to the massive woman administering the shot.
“Yes, child. You’ll should see results very soon.”
You get off the table, and try to stand, woozy from the shot you just got.
“Try to get some rest in your room. The changes will be sudden, and will drastically affect your body for the next couple weeks.”
Back home…
You groggily drag yourself out of bed, feeling sick. As you balefully stare at the mirror, bags under your eyes, you notice the immediate change to your body.