Ten years ago, "the Gate", which connected the real world and the monster world, was opened. Some ordinary people were granted the ability to hunt monsters within this Gate. These people are called "Hunters".
Not all Hunters are equally powerful. Sung Jin-Woo is an E-rank Hunter. He is someone who must risk his life in the lowest of dungeons. He had no skills to show so he struggled to earn the money. Until he discovered a hidden dungeon that was the most difficult within the D-rank D-rank dungeons.
As he was about to accept death, he received an unusual power. It was a quest log he couldn't see. This gave him a secret way to level up. His level would increase if he followed his quests and hunted the monsters. He can go from being the weakest Hunter to becoming the strongest S-rank Hunter.