Having entered the instance dungeon located inside the subway, Jinwoo levels up time and time again by fighting waves of magic beasts. As he gradually makes his way forward, he finds a long stairway leading deeper underground.

Jinwoo joins a party led by Hwang Dongsuk to meet the headcount necessary for a C-Rank dungeon. Joined by another temporary hire, Yoo Jinho, the party defeats beasts without much trouble, but Jinwoo has suspicions about the group's lack of a healer.

As Jinwoo continues his training, he completes a daily quest one day by doing more than the quest requires, and a key that leads to a certain item appears in front of him.

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.