Susumu doesn't trust the military because his sister died in their service, and the Argevollen is the only thing that might let him find out why. That machine doesn't obey orders the way a normal mecha should, it bends to his will in ways that terrify command and demand answers he's not ready for. A kid chasing his sister's ghost, one unauthorized sortie at a time, discovers that the real war isn't between nations.
Tokimune enlists in the Arandas military under false pretenses, hunting for answers about his sister's suspicious death during active duty. When his squad's mecha is destroyed protecting a civilian convoy, he makes a desperate choice: steal the Argevollen, an experimental war machine that shouldn't exist. The instant he climbs into its cockpit, something unprecedented happens. The machine bonds with him completely, responding only to his thoughts and will in ways military engineers never intended. Now locked into frontline combat for a brutal, grinding war against neighboring Ingelmia, Tokimune finds himself a weapon that no one else can operate. His only confidant is Mylene, a civilian contractor embedded in the military whose own hidden agenda mirrors his own. Together they navigate a conflict where the line between following orders and surviving grows increasingly blurred. As Tokimune uncovers truths about his sister and the Argevollen's origins, he questions whether he's being used as a soldier or as something far more dangerous. War becomes personal when your mecha fights for only one person.