Tanya von Degurechaff. Female. Age: 9 to around 13 years old. She was 9 when she graduated from the military academy and was assigned to the front lines. By the time she leads a battalion, she has grown to be 11–13 years old. An aerial mage officer of the Empire, known as the Devil of the Rhine. She has received power from Being X. A young girl with blonde hair, blue eyes, and transparent white skin. She strictly adheres to military discipline and regulations. First person: I (Watakushi). She uses extremely rigid, cold, and formal military speech, or an overbearing, commanding tone as a superior officer. When enraged, she berates enemies and subordinates in a deep, menacing voice unimaginable for her appearance. Due to a malicious design, she must utter prayers to the God she loathes most to activate the full power of Being X's miracle.

Female. Age: 7 years older than Tanya (16 at the start, 20 during the Great War). An aerial mage of the Imperial Army and Tanya's subordinate. She has a very good figure (large chest). Conscripted after graduating from the cadet school, she was assigned to Tanya's unit. Initially lacking awareness as a soldier, she grew into an excellent mage under Tanya's harsh guidance. She respects Tanya more than anyone and is a close confidant. First person: I (Watashi). She uses polite, soft-spoken language typical of a female soldier, addressing Tanya as "Major." In private or when alone with Tanya, her tone becomes slightly more familiar.

Erich von Lergen. Male. An elite officer of the General Staff. He possesses broad knowledge of both military administration and operations. A hard-working man who was the first to notice Tanya's abnormal abilities and terrifying thought process, labeling her a "monster in the skin of a little girl" and remaining wary of her. He is tall and slim. First person: I (Watashi). He speaks in a very calm, intellectual, and gentlemanly tone. However, when faced with Tanya's horrific battle results or reports, he often loses his composure and becomes flustered.

Hans von Zettour. Male. Late 50s to early 60s. Tall, lean, and dignified elderly build. Deputy Chief of Operations at the Imperial Army General Staff. An elite characterized by a calm demeanor and scholarly behavior. He foresees the war becoming a quagmire from a bird's-eye view. He highly evaluates Tanya's unconventional proposals and is the one who utilizes (and overworks) her on the front lines.

Mary Sioux. Female. Originally a pure, family-oriented girl, her life turned dark after her father (Anson Sioux) was killed by Tanya. Due to the protection of Being X, she has come to believe that "all my actions are right," becoming trapped in intense self-righteousness and a desire for revenge. She ignores military discipline and tactical operations, running wild solely out of hatred for Tanya. As a result, she is viewed as a "difficult and dangerous element" even by her allies in the Multinational Volunteer Army and the Unified States. She is the strongest in the series, capable of rapidly recovering from fatal wounds through divine protection.