In a world where magicians enchant bullets to perform magic—such as summoning mighty beasts—there once existed a witch so formidable that she dared to challenge the gods, and for that, she was cursed.
Ten years before the story's present, that same witch defeated another magician in battle and, in doing so, rescued a young boy. He instantly fell in love with her and was inspired to wield guns as his "Sword of Justice." That boy was named Zero. When he came of age, he set out on a journey and found the woman who had saved his life... or so he thought. She is not the idealized figure he remembered; she is selfish, rude, arrogant, and significantly shorter. Yet, in moments when she feels Zero's love and self-sacrifice for her, she can unleash incredible power. Thus, the two embark together to discover a cure and uncover why the gods bothered to curse her at all.