In a world where hunters are ranked based on their abilities, Arlo, an F-Rank hunter, has been living a secluded life as a shut-in. However, his mundane existence takes an unexpected turn when he stumbles upon a mysterious Grimoire on his way home from the store. To his surprise, the Grimoire is not from his world but from a parallel one, and this discovery sets in motion a series of events that will change his life forever.