Kōji Tanita is a sergeant in the Arandas Army's 8th Independent Unit. He serves as an infantry soldier whose primary duty is ground support for the unit, and he is specifically in charge of overseeing backups and coordinating rear-echelon operations. As a non-commissioned officer, he is generally reliable and responsible, though he occasionally shows an absent-minded or careless side. This is illustrated by an incident during a brief rest in the town of Wishepe, where he suffered food poisoning from river fish and was temporarily unable to fulfill his command duties. Tanita’s motivation is rooted in fulfilling his role as a dependable support soldier for his comrades, but his character does not undergo significant personal development over the course of the story. He interacts with the main cast as part of the unit’s collective, providing logistical and infantry-based assistance rather than piloting a Trail Krieger. His notable abilities lie in his organizational skills managing backups and his competence as a frontline infantryman, though he lacks any unique combat or technological talents.