Kondaku no Shinkon

One day while walking home from school, a girl falling from above crashes into the protagonist. He wakes up inside the hospital few days later but the girl, Yukine, does not. However, it seems that their minds have been mixed and something strange happens to his body. It's female when he is in charge and male when Yukine is. And thus begins their struggle against everyday life with 2 mind in 1 body.