One day, faint-hearted Hyeonbok Kim opens his apartment door and is startled to find a dungeon full of monsters instead of the world he knows. At first he hides. But when all else fails, it falls to Hyeonbok to defeat the dungeon bosses or die trying. Luckily, he's not alone. With the help of his skeleton friends (and a gift from a mysterious benefactor), he develops his rare talent for magic while learning about bravery and friendship. Hyeonbok seems ready to face whatever the dungeon throws at him... but is he?