Doll-Kara

Kazuyoshi Ishii, the founder of the martial arts organization K-1, had been sent to prison for tax evasion. After serving his sentence, he exits Shizuoka Prison only to be immediately killed by a speeding truck and reincarnated in the body of Kei Ichinose—a comatose high school girl?! Twenty years since the genesis of K-1, the MMA world's problem solver now inhabits the body of a schoolgirl and comes to grips with the karate he left behind in this story of youthful spirit and determination.

(Source: J-Novel Club)