About a decade ago, "gates" began to open and connect this world to different dimensions. "Awakened Beings" started to appear among ordinary citizens. These "Awakened Beings" are the only ones strong enough to fight the monsters in the dungeons beyond each gate. They are called "hunters." However, not all hunters are created equally. One E-Rank hunter they call "The Weakest Hunter of All Mankind" struggles to stay alive, even in the lowest-level dungeons. His name is Sung Jinwoo. With almost nothing to his name, he braves the dungeons to support his family and barely makes enough to get by. At least until he finds himself in a deadly "Double Dungeon," hidden inside a lowly D-Rank gate. Believing it's the end, he accepts the inevitable... ...But awakens to discover new and strange abilities. A quest window, like one from a video game- only visible to him! And with it, a secret means of "Leveling Up!" He now seeks to "level up" by hunting monsters and completing these quests... ...that can only be done solo!