In a world where Espers are either soldiers or sacrifices to hold back the Demon King, Valencia is dismissed as a “useless” F-rank Guide. Hiding in the slums, she conceals a dangerous truth—her Void power—and dreams of living a quiet, ordinary life. That dream shatters when she crosses paths with Kael, the Duke’s son and an S-rank Light Esper who has been unraveling after eight years without a Guide. Unaware that only Valencia can anchor him, Kael becomes dangerously drawn to her, while she struggles to keep her secret buried. Forced into a role she never wanted, Valencia must survive a society that fears her and a Royal Family determined to erase the slums. But when the palace discovers she is a Void Esper, she is thrust toward a fate tied to the Demon King itself—where love is forbidden, and power is a curse.