Ten years before the story begins, gates connecting the human world to dungeons filled with monsters began appearing across the globe. Alongside this phenomenon, a small percentage of the population awakened supernatural abilities, becoming known as hunters—the only people capable of entering these gates and clearing the threats within. Hunters are ranked from E to S, with S being the most powerful.

Sung Jinwoo is an E-rank hunter, infamously called the weakest hunter in all of South Korea. Barely stronger than a普通 human, he risks his life raiding low-level dungeons to pay for his mother's hospital bills, as she suffers from a mysterious illness, and to support his younger sister's education. During a routine raid inside a D-rank gate, his party discovers a second, hidden passage leading to a temple. Ignoring ominous statues and commandments, the group triggers a trap. To allow the others to escape, Jinwoo is left behind as a sacrifice, facing certain death. As he bleeds out on the temple floor, a holographic blue window appears before him, asking: You have acquired the qualification to be a Player. Do you accept?

Upon accepting, Jinwoo wakes up in a hospital with access to a mysterious System, a video game-like interface only he can see. Unlike every other hunter whose power is fixed from the moment of their awakening, Jinwoo can now complete quests, earn experience, and level up his stats indefinitely. His first mandatory quest, a brutal daily workout, tests his resolve, but he quickly realizes this is his only chance to change his fate. As he levels, his physical appearance begins to change, and he becomes more powerful, but also more logical and detached, discarding some of his former empathy for a ruthless efficiency needed to survive.

The story follows Jinwoo as he navigates this new reality, beginning with soloing instant dungeons and quickly rising through the ranks. He forms a crucial partnership with Yoo Jinho, a newly awakened but sincere rich kid from a powerful family who becomes his loyal second-in-command. Together, they navigate the dangerous world of guild politics and monster hunting. The narrative progresses through several major arcs, from the betrayal and revenge of the Dungeon & Prisoners Arc to the pivotal Job Change Arc, where Jinwoo gains the unique Necromancer class, allowing him to raise defeated enemies as shadows that serve him eternally.

As his power grows to S-rank and beyond, Jinwoo faces increasingly dire threats. The Jeju Island Arc sees him single-handedly turn the tide against a devastating ant swarm that had previously decimated Korea’s S-rank hunters. He eventually establishes his own guild, the Ahjin Guild, to better control his operations. Seeking answers about the System, he returns to the Double Dungeon where he nearly died, confronting the Architect who created the System under orders from the Shadow Monarch, one of several god-like beings known as Monarchs.

The final third of the series escalates into a war between the Monarchs, who seek to destroy humanity, and the Rulers, who wish to protect it. After resolving a major crisis in Japan, Jinwoo attends the International Guild Conference, where he formally reveals his power to the world. The Monarchs launch their full invasion, leading to the Monarchs War and a final apocalyptic battle against Antares, the Monarch of Destruction. Using the Cup of Reincarnation, Jinwoo turns back time to just before the gates first appeared. In this new timeline, he defeats the Monarchs permanently before they can threaten the world, sacrificing his memories in the process. The story concludes with Jinwoo living a peaceful, happy life with his family and friends, though he eventually recovers his memories and his powers as the sole ruler of the shadows.