"Girls und Panzer: Little Army" is a prequel manga to the "Girls und Panzer" series, focusing on Miho Nishizumi's early experiences with tankery during her middle school years. The story begins with Miho transferring to Kuromorimine Girls' Academy, a prestigious school renowned for its tankery program. Despite her family's legacy in the sport, Miho initially struggles with the expectations placed upon her as a member of the Nishizumi family, known for their mastery of tank warfare.

At Kuromorimine, Miho joins the school's tankery team, where she meets and befriends key characters such as Erika Itsumi, a disciplined and competitive teammate, and Maho Nishizumi, her older sister and the team's commander. The narrative explores Miho's growth as she learns to navigate the pressures of her family's reputation while developing her own approach to tankery. The story highlights her internal conflict between adhering to the strict, traditional tactics of the Nishizumi style and her desire to prioritize teamwork and camaraderie over rigid discipline.

The manga delves into Miho's participation in training exercises and competitions, showcasing her evolving skills and leadership abilities. Key moments include her first experiences commanding a tank, her interactions with teammates, and her gradual realization that tankery can be both a competitive sport and a means of forming meaningful connections. The story also provides insight into the dynamics of the Nishizumi family, particularly the strained relationship between Miho and her mother, Shiho, who embodies the uncompromising ideals of the Nishizumi tradition.

"Girls und Panzer: Little Army" serves as a character-driven exploration of Miho's formative years, setting the stage for her eventual departure from Kuromorimine and her later involvement with Ooarai Girls' Academy in the main series. The manga balances action-packed tank battles with personal drama, offering a deeper understanding of Miho's motivations and the challenges she faces in reconciling her individuality with her family's legacy.