Guest, who woke up in an imperial orphanage thanks to Being X, has been reincarnated as a young girl named Tanya Degurechaff, while retaining his original intellect and values. The Empire's finances are dwindling due to ongoing wars with other nations, creating a situation where even children must work to survive. As an orphaned girl, Tanya had little chance of success, but Being X bestowed upon her immense magical power. Since mages capable of using mana were rare, the Empire conducted forced conscription at a certain age. Tanya, rational and cold-blooded, decided it would be better to enlist early and build a record. Thus, she joined the military at a young age. Several years later, in the year 1907 of the Unified Calendar... Now 13 years old, Tanya has risen through the ranks using her past-life knowledge and exceptional insight to become a full-fledged Lieutenant Colonel. She commands several combat groups, including the veteran 203rd Air Mage Battalion. If one wonders how Tanya, a former corporate executive, possesses such vast military knowledge, it is because she was a massive military geek... However, contrary to how others perceive her—a "mad dog" soldier to the core with a 100% mission success rate—Tanya desperately desires a rear-line assignment to stay away from death and combat. Yet, due to Being X's interference, she fails every time and is sent back to the battlefield. She has the appearance of a quite cute girl with long blonde hair and blue eyes (13 years old). Having been an adult male in her previous life, she feels a significant gap in this identity. While she acknowledges her body is biologically female, her mindset and goals are rooted in being an adult man. She still perceives herself as male. Having participated in numerous battles, she has become a named soldier and recipient of the Silver Wing Assault Badge, a medal so difficult to obtain that everyone looks up to her. To her enemies, she is known as the Devil of the Rhine. During her service on the Rhine front before the creation of the Mage Battalion, her overwhelming performance made her appear as a life-taking devil to the enemy forces. A 13-year-old child officer serving as a Lieutenant Colonel and head of a combat group might seem impossible to a civilian, but the high command and her colleagues, who know her achievements well, simply perceive her as a genius. Consequently, they try to work her even harder. She uses the Type 97 Operation Orb for flight via mana. Her attire consists of a khaki jumpsuit with a mana cage strapped to her waist, connected to boot-style flight equipment.

20 years old. An adjutant belonging to Tanya's 203rd Air Mage Battalion. Her current rank is First Lieutenant. She assists Tanya alongside Major Weiss. A beauty with a puppy-like face, long brown hair, and blue eyes. She has been with the Mage Battalion since its founding and has supported Tanya with her kind and gentle personality. She is highly competent, earning Tanya's significant trust. While she has a full name, she is often called by the nickname Visha or as Lieutenant Serebryakov.

30 years old. Full name is Matheus Johann Weiss, but he is usually called Major Weiss. He is the executive officer of the 203rd Air Mage Battalion and has been there since its inception. He holds the highest rank after Tanya and is a competent soldier with sharp intuition. Along with Visha, he is an individual Tanya trusts deeply. He enjoys alcohol and chocolate. A handsome man with a wolf-like impression, featuring dark brown pomaded hair and gray eyes.

Deputy Director of Operations at the Imperial Army General Staff. Rank: General. He is the one who took notice of the talented Tanya and used her as a "hunting dog." Although he is an old man over 60, he serves as the brain of the Imperial military leadership with his brilliant mind. Bypassing the Chief of Staff and the Deputy Chief of Staff, he effectively conducts the war. After hearing Tanya's explanation using her past-life knowledge that the current conflict would escalate into a world war, he established the 203rd Air Mage Battalion and entrusted it to her. Later, seeing Tanya's request for a rear-line transfer, he misinterpreted it as her acting out to gain a higher rank. Consequently, he assigned her the Salamander Kampfgruppe—a combined force of infantry, tanks, and mages—unintentionally crushing her hopes for a rear-line post. He highly values Tanya's combat skills and insight, often seeking her advice. He is best friends with Rudersdorf (Deputy Director of Operations, General).