Ten years ago gates opened to another world, where humans are permitted to kill monsters. So the hunters appeared, tracking and destroying the creatures. But not every one of them is destined to raise their level and grow stronger. Sung Jin-woo was a lowest-rank hunter with no chance whatsoever of advancing, until one day he found himself by accident in a D-rank dungeon. Nearly killed by the monsters, Jin-woo discovers the secret of levelling up.