While Tanya Degurechaff may look like a cute, adorable and innocent little girl, but deep inside, she is a cold-hearted and ruthless contractualist. This side of her is especially evident when she is in battle against her enemies; she shows no remorse as she weaves through a chaotic battleground inflicting maximum damage through whatever means necessary to accomplish her missions. Tanya strongly disapproves of failure and disobedience from her subordinates. She is loyal to her own job and always wants to finish it as soon as possible. Tanya will never let anyone discriminate against her appearance because of how fast she goes through the ranks in the military.

Tanya was originally a male salaryman who was murdered by a coworker after he fired them. Tanya was reborn as a young girl living in an alternate universe version of Europe during World War I. At just nine years of age, to avoid conscription into less work, Tanya volunteers for the Empire's Mages Division and is promoted to Second Lieutenant shortly after.