The protagonist, known by the handle SR, is the top player of the VR MMO game Tempest. After ten years of dedicated play, he becomes the first person in the world to solo-clear the game's final dungeon. Immediately after achieving this feat, he is reincarnated into the very game world he was just playing. He awakens in the kingdom of Lindell, summoned as part of a hero summoning ritual, but finds himself at level 1 with the job class of Unemployed rather than Hero. The king, desperate, explains that his daughter, First Princess Phenon, has only one month to live due to a mysterious illness, and the only cure is a rare elixir that can be obtained by clearing a B-rank dungeon. Despite his low level and lack of a heroic class, SR accepts the quest, relying on his encyclopedic knowledge of the game's mechanics, enemy patterns, and item locations.

SR quickly adapts to the now-real world, leveraging his knowledge to level up efficiently. He forms a partnership with Sera Bellnot, a proud and competitive noblewoman and knight who initially clashes with him but comes to respect his skill. Together, they form a party with additional members including Princess Phenon herself, who after being cured joins the party to pursue her own dream of exploring dungeons, and her attendant Shii. The group faces a series of dungeons of increasing difficulty. A major early arc involves securing the elixir within a strict time limit, culminating in a desperate battle against the B-rank dungeon's boss in which SR triumphs despite exhaustion and injury. After saving Phenon, SR is granted the official title of Hero by the kingdom, though he continues to deny being one, setting his sights on a different ultimate goal: the secret third-tier job class known as the Demon King, which he believes is the true pinnacle of power in this world.

A notable narrative arc follows Sera's personal struggle. Her older brother, Rei, a powerful and domineering explorer, challenges her to a martial arts tournament, threatening to force her to quit adventuring if she loses. With SR's coaching and a strategy that conceals her true abilities until the final moment, Sera overcomes her childhood trauma and defeats Rei, securing her freedom to continue her adventuring life. This victory also leads SR to reveal the existence of the Demon King job class to his companions. Another major arc begins when the party travels to the neighboring country of Ryuto, a theocratic nation dominated by the Dominus faith. To gain access to the A-rank dungeon within Ryuto, SR negotiates with the queen, agreeing to provide a hundred elixirs in exchange for entry. The party faces religious and political obstacles, including an assassination attempt by zealous followers of the Dominus faith, and builds a log cabin near the dungeon to facilitate repeated runs. During this arc, a new character, Mikage, is assigned as an overseer, and a romantic triangle develops as both Sera and Mikage vie for SR's attention.

The story escalates when, after clearing the A-rank dungeon, Mikage is stabbed by an unknown assailant. In the confusion, SR encounters Noah, the creator of the VR world, who reveals that the game world is on the verge of collapse and that the only way to prevent disaster is to clear all the remaining dungeons. This shifts the narrative from a personal quest for power to a mission to save the entire world. SR accepts the challenge, but now operates under the constraint that death in this world is permanent, unlike in his former game. He begins a systematic campaign of grinding B-rank dungeons for rare drops and leveling his teammates, while Sera and other allies tackle A-rank dungeons with his guidance. The story continues to unfold across new territories, with SR maintaining his role as a strategist and mentor who insists he is not a hero even as he becomes increasingly central to the world's survival.