Over a decade has passed since a pathway called a "gate," which connects this world and another dimension, suddenly appeared, and people with superhuman powers called "hunters" have been awakened. Hunters use their superhuman powers to conquer dungeons inside the gates to make a living, and Sung Jinwoo, a hunter of the lowest rank, is considered the Weakest Hunter of All Mankind. One day, he encounters a double dungeon, a high-level dungeon hidden inside a low-level one. In front of a severely wounded Jinwoo, a mysterious quest window pops up. On the verge of death, Jinwoo decides to take on the quest, which makes him the only person who can level up.

[Source: Crunchyroll]