Jinzou Shoujo(2000)

Jinzou Shoujo

A scientist finds a brain in an alley and implants it into the body of his beloved, Nina. It turns out the brain belonged to a boy, Misumi Yutaka, and he is none too happy to find himself in a female body. What happened to Yutaka's body and why was his brain in the middle of an alley? What will happen to "Nina" when the female parts of "her" body start to have an effect on "his" mind? You'll have to read to find out.