Tanya von Degurechaff

Tanya von Degurechaff is the main protagonist of the light novel/anime Youjo Senki: Saga of Tanya the Evil. Originally a salaryman who died in an accident in 2013, he was reborn as a girl living in an alternate universe version of Europe during World War I.

At just nine years of age, Tanya enters the Empire's Mages Division and is promoted to Second Lieutenant. Her talents, efficiency, and ruthlessness makes her an asset for the Empire and a threat on the battlefield.

Since she graduated from the War College as one of the twelve knights, she's granted the title of von.

Trivia
Tanya Degurechaff was compared to the Fallen Hero of Germany named Manfred von Richthofen a.k.a Red Baron. Both of them are considered as "Aces of Aces" during their own World War.