By the close of the 21st century, humanity had uncovered a novel power source called DG energy—short for divine grace energy—that transformed the planet"s economy and opened the door to space colonization. Yet when the first mission reaches Pluto, they are ambushed by a colossal unknown organism dubbed Nergal.
In response, the Earth Alliance Army develops an AG Unit by repurposing ancient robotic constructs known as G"s Frames, recovered from archaeological digs worldwide. Only girls with unique attributes, the Ancient Girls, can command these machines against Nergal. The inaugural AG Unit suffers devastating losses during the Jupiter Trojan campaign, and pilot Minamiya Reiu of Unit 04 disappears in action.
Years later, her younger sister Minamiya Reika joins the AG Unit to locate her missing sibling and defend Earth from Nergal. The tale unfolds with camaraderie, relic mecha, and deadly clashes against the alien menace. Their quest is fraught with peril as the Nergal's power grows, and the ancient machines must be upgraded to survive.
