Natsume, a teenage girl, loses her father and right arm in a childhood Gadoll attack, forging her resolve to join the warrior class Power and eradicate the Gadoll threat. Assigned instead as an armor repairer under Kaburagi—a former warrior turned maintenance supervisor—she adapts to her prosthetic arm, later upgraded by him into a weapon launcher customized for her combat style. Her rapid mastery of combat training surpasses human norms, achieved by weaving the prosthetic’s mechanics into her techniques rather than treating it as a shortcut. Defiance of limits fuels her approach to challenges.

Her relationships evolve dynamically: Kaburagi transitions from strict superior to mentor and pivotal ally, while tensions with friend Fei over divergent views on their roles in Deca-dence test but do not sever their bond. Kurenai, a revered Tanker fighter, becomes a role model, sharpening Natsume’s ambitions.

Designated a “bug” due to a system error falsely marking her deceased, her existence defies Deca-dence’s cyborg-controlled hierarchy. Kaburagi shields and trains her against corporate directives, propelling her into resistance against Solid Quake’s oppressive governance. Discovering Deca-dence’s truth as a cyborg entertainment construct fractures her worldview, yet she persists, galvanizing Kaburagi to shed apathy and reengage in the fight. Together, they disrupt systemic inequities, reshaping Deca-dence into a fairer society for humans and cyborgs.

Her arc intertwines physical and emotional resilience—navigating loss, disability, complex bonds, and rigid structures—while shifting from personal vengeance to collective liberation. This progression cements her role as a catalyst for systemic change, challenging both mechanized tyranny and complacency within the narrative’s core.