Intrigued by the severe lack of faith a particular salaryman displayed as he drew his last breath, a godlike presence known only as "Being X" reincarnates him into a magical yet war-torn world to test his mettle. Under these new circumstances, Being X believes that, should this man succumb to relentless suffering, he will call upon the heavens for assistance.

Starting life again as a young girl named Tanya Degurechaff, the salaryman quickly utilizes his past experiences and volunteers for the military of his country, the Empire. Wielding tremendous potential despite being a child, Tanya's prodigious capacity for strategic and magical warfare allows her to quickly ascend the ranks and consistently lead her nation to miraculous victories in the ongoing war. Even so, she does all of this for one purpose: to live in the backlines far from the war zone, effectively defying Being X's objectives.

However, as Tanya strives to escape Being X's influence, she soon comes to know that even with her genius, there are situations that a human simply cannot overcome without divine intervention.