The protagonist, Fujimura Akito, a 32-year-old salaryman, finds his life drastically altered when a mysterious brick structure suddenly appears on his property. Exhausted from overwork, he initially dismisses it as a prank or hallucination. However, upon entering the structure, he is transported to a place called the "Infinite Corridor" and is identified as the first player for its beta test. He encounters a goblin, which he easily defeats, gaining experience and a "Goblin's Club." This event triggers a system notification, revealing his stats and granting him the "Tree of All Systems" ability.
Following this, Akito is attacked by a horde of goblins, forcing him to barricade the entrance to the Infinite Corridor with household items. The next morning, he discovers his stats have appeared in a game-like interface, identifying his race as "Salaryman." He learns that monsters have begun appearing worldwide, causing casualties. Akito's company, Araragi Electronics, is researching the "miracle black stones" dropped by monsters, which are proving to be a potent energy source. He also interacts with his younger colleague, Amamiya Azusa, a 24-year-old with a childlike appearance, who is an ace in the R&D department.
A major turning point occurs when Akito and Azusa are caught in a monster attack at a hamburger shop. A powerful "Orc" appears, brutally killing civilians. Akito, despite his fear, manages to protect Azusa. The incident deeply shakes him, making him realize the need to become stronger. He decides to train in the Infinite Corridor, using a crossbow and axe to hunt goblins. Through this, he levels up, his stats improving significantly, and he gains new skills like "Salaryman's Bag" and "Salaryman's Eye," and the title "Model of a Salaryman." He also gains the ability to rank up his race, choosing "Chicken Hunter" for its focus on evasion and ranged combat.
Akito's sister, Akari, visits and expresses concern about his well-being and his involvement in the monster incident. She reveals that his family knows about his situation, and he reassures her, promising to pick her up from school. He then returns to the Infinite Corridor, progressing to the second floor where he encounters "Two-Headed Chickens." He continues to train, leveling up and acquiring a "Shame Ring" from a treasure chest, which boosts stats based on embarrassment.
Meanwhile, a government meeting discusses the increasing monster appearances and the strategic importance of the black stones. The establishment of a monster-hunting organization is proposed. Akito, now a "Chicken Hunter," continues his training, aiming to become strong enough to survive in this new, dangerous world. He also encounters a high school student who initially appears to be a middle schooler, leading to a humorous misunderstanding and a display of her surprising strength. Akito's journey is driven by a desire for an easier life, but the escalating monster threat forces him to confront his fears and actively pursue strength.
