June 1923 of the unified calendar. A young girl with blond hair and blue eyes, Tanya Degurechaff, is training for the final course of the Imperial Military Academy at the third patrol line of the Norden Theater in the northern military district as part of her service. The training, which took the first step towards a glorious career as an aviation mage, ended peacefully - or so it should have. But things took a turn in an unexpected direction. Taking the cross-border invasion of the Allied Union as an opportunity, the Empire and the Allied Union entered a state of war. With the transition to a wartime system, Tanya was given an observation mission, but the Allied Union launched a surprise attack, and Tanya was forced to fight alone with the enemy's mage squadron. The enemy is numerous and we are few, and we can't even contain the enemy before our army arrives, but if we run away, we will inevitably be sentenced to death for fleeing in front of the enemy, and she faces this desperate situation. In order to survive anyway and to do the best job when facing the top, Tanya used a certain strategy... "That is a monster in the skin of a young girl--."