F-class tactician Akito visits his new lord with his summoned master pieces, the slime "Rin" and the golem "Benke", but the only 10-year-old girl, Sule, appears there. . A frontier land ruled by Sule, Arstatt is an “abandoned land” surrounded by demon lord territory and on the front line without reinforcements. In a town that has lost order, human trafficking is rampant, and the Demon King's army is approaching right there. Tactician Akito stands up with his mentor to survive the desperate situation...