In a distant era, the creature species called Gadoll emerged abruptly as humanity"s greatest danger. The few remaining humans on Earth retreat into the Tank, a lower quarter of the enormous mobile citadel Deca-Dence. While the Gears who dwell on the upper levels are fighters dispatched as part of the Power, most Tankers prefer to stay behind, slaughtering Gadoll flesh and bolstering defenses. Natsume belongs to those who wish to fight at the front; despite her prosthetic right arm, she yearns to join the handful of Tanker soldiers who accompany the Gears into battle. They maintain the fortress"s infrastructure, repairing armor and fortifying walls.
Yet, although every orphanage resident receives a job assignment, Natsume"s request to join the Power is denied. In the interim she takes a cleaning post in an armor‑repair crew commanded by the stern, indifferent Kaburagi, who hides deeper motives. Initially aloof toward his earnest junior, he soon sees in her the spark capable of shaking the world"s order. Her resolve turns her into an unlikely hero. Amid the constant threat as they fight for survival. As her new guide, Kaburagi readies her for a singular, pivotal role that will become the system"s disruptive catalyst.
