A colossal creature emerges from the depths to attack Tokyo, prompting ASY, Japan's peacekeeping force, to deploy their secret weapon: a mechanical faery capable of devastating power. Victory comes swiftly, but triumph shatters when a radiant girl materializes in the sky and unleashes a blinding beam of pure light. Her name is Rouran, though "name" feels generous for something she barely understands about herself. No memories exist before this moment. No understanding of why her body glows with otherworldly energy or transforms into something divine and destructive whenever Kyoushi reanimated corpses surface nearby. Every instinct screams that these creatures demand her rage, but she cannot fathom why. Tetsuya takes her under his wing in Tokyo Arcadia, a sprawling settlement where refugees and outcasts build new lives far from society's rules. There, amid the displaced and forgotten, Rouran searches for answers about her nature while shadowy forces continue their assault on the city. Each battle pulls her closer to understanding the truth, but every revelation births new questions about what she truly is.