Youjo Senki
Comic book
A young girl fights on the frontlines in war. She has blonde hair, blue eyes, and nearly transparent white skin, and she flies through the air and mercilessly strikes down her opponents. Her name is Tanya Degurechov, and she speaks with a young girl's lisp and commands the army. Tanya used to be one of Japan's elite office workers, but because of a wrathful god, was reborn as a little girl. Tanya prioritizes optimization and career advancement above all, and she will become the most dangerous entity among the Imperial Army's sorcerers.
English
https://manganelo.com/manga/youjo_senki
Novel
A male protagonist died and reincarnated into a parallel world as a girl at the age of the first World War. But there is magic in the parallel world.
English
https://www.novelupdates.com/series/youjo-senki/
Japanese (日本語; にほんご)
http://www.mai-net.net/bbs/sst/sst.php?act=dump&cate=tiraura&all=24734