Hyoufuu no Kolkka: Yuki no Yousei to Shiroi Shinigami

Year 1939. Neuvosto Union (Venäjä Army) started invasion on small Republic of Suomi with intention to claim its territory. Armed with marksmanship skills and disguised as a man, boastful pretty girl Kolkka joins Suomi military to protect her homeland against Venäjä Army. She gets assigned to platoon of company commander Juutilainen, where she meets Simo Häyhä, nicknamed "the White Death". Using bold attack attempt by Juutilainen and superhuman sniper skills of Häyhä Venäjä's large army gets slaughtered.
Boastful Kolkka rapidly grows as a genius marksman thanks to her tremendous sense and inborn, strong-minded personality. Soon in front of Häyhä and Kolkka stands Venäjä Army's most dangerous woman snipers, Natalia and Misha!
Taking place in the historical war of aggression "Winter War" a story of ultra-strong genius sniper girl is born.
(Source: original description, AR15.com)