Youjo Senki

On the battlefields, it sometimes happens that a young girl appears. She has blond hair, blue eyes, and extremely pale skin. Thanks to her supernatural powers and with the help of the troops under her command, she mercilessly exterminates enemies who cross her path. Her name? Tanya Degurechov. She is in fact the reincarnation of a man who, before his death, was part of Japan's elite.

Here is the description and origin of the one considered to be the most dangerous person in the Imperial Army...