Around ten years ago, gates that connected our world to another dimension began to appear, leading to the rise of hunters who would traverse these gates to fight the magic beasts within. Sung Jinwoo, E-Rank hunter, is the weakest of them all.

Out of the blue, a "job-change quest" pops up in Jinwoo's window. Feeling that it may help him get stronger, he enters the gate. Inside, he fights wave after wave of enemies, culminating in a knight who brings back memories of the Cartenon Temple.

Drained from endless battle, Jinwoo sees a phantom of his past self. To overcome his own past as the Weakest Hunter of All Mankind, he struggles to find a way to clear the job-change quest.

Having completed his promise to Jinho to clear 19 dungeons, Jinwoo is stronger than he was when he fought the Cerberus. In order to gather the ingredients for the Elixir of Life and save his mother, he once again enters the S-Rank Demon's Castle dungeon.

Jinwoo realizes that he'll need to become even stronger in order to clear the Demon's Castle and decides to have his hunter rank reassessed.

Seeking the remaining ingredient for the Elixir of Life, Jinwoo continues his conquest of the Demon's Castle.