"Kill the boss of 4th floor or your entire family will die." For most, dungeons are a great source of expensive goods. For others, it's a place where they can grow their strength. But for Arthur, his one-of-a-kind, personal dungeon only brought grief and emptiness. Drastic penalties for failing the missions aside, why is Arthur's personal dungeon the only one in the world that can lead to its owner's death?!