The story begins with Aao Segawa finding himself in a blank white space, addressed by a disembodied female voice. He learns he has "normally died" from sudden cardiac arrest while on his usual train commute to school. The voice, which can read his thoughts, shows him his own death: he was asleep on the train, leaning on an elderly man, and his body is visibly lifeless. His death causes a panic on the train, leading to injuries and a national news event, which is later revealed to be a false alarm. The ensuing public fascination with the cause of the commotion leads to Aao's personal information being leaked online, causing him immense distress and guilt towards his family.
The mysterious voice reveals she brought his soul to the boundary between the living and the dead. She explains that while she cannot resurrect him, she can send him to another world. This world is described as one of magic and swords, where strength is paramount. Aao, fearing for his survival without any combat experience, asks if he will receive any "cheat" abilities. Instead, he is granted "language comprehension," which he finds underwhelming and insufficient for survival. The voice, seemingly indifferent, states it's a manual decision and then, with a dismissive attitude, sends him off to the new world.
Aao awakens in a large room, surrounded by people who regard him with suspicion, some even drawing swords. A stern man, seemingly the king, demands his name. Aao's blunt observation that the king should introduce himself first causes further unrest. Despite the tension, the king laughs, only to then order Aao's execution. A young woman, revealed to be the princess, intervenes, arguing against the execution for the sake of the hero summoning ritual. However, the king remains resolute. As guards approach, the princess pleads with them, but they are bound by the king's command. The princess then directly confronts the guards, proclaiming Aao is their hero.
Suddenly, the guards' swords are deflected as they strike Aao. The mysterious voice from before speaks into his mind, revealing that she granted him a cheat ability: he will not be harmed or fall ill until his natural lifespan ends. This grants him near invincibility, though he lacks offensive capabilities. Aao, now confident in his survival, declares his intention to become a NEET (Not in Education, Employment, or Training) in this new world. He walks past the guards, who are unable to harm him, and is then approached by the princess, who, despite his claims of not being a hero, implores him to help their country. Aao, however, is focused on his NEET goal and proposes that the princess become his maid.
The princess, Liliria, agrees to accompany him, and they escape the castle. They travel towards the country of Rooji, planning to avoid capture. Aao, realizing he needs money to live as a NEET, forces Liliria to pawn a brooch to fund their journey. During their travels, they encounter a group of monsters, which are swiftly dealt with by Liliria, who reveals herself to be a powerful adventurer, though she claims to be incredibly unlucky. Aao, protected by his invincibility, is thrown into the fray by Liliria and easily withstands the monster attacks.
Later, a dragon attacks their carriage. Liliria, despite her bad luck, is a formidable fighter and engages the dragon. Aao, using his language comprehension ability, discovers the dragon can speak and is drawn to strength. The dragon offers Aao a scale to visit its village, but Aao declines, prioritizing his NEET lifestyle. The dragon also expresses interest in Liliria, finding her strong and worthy of bearing its offspring.
Upon arriving in Rooji, Aao and Liliria meet Silha, the adventurer who fought the dragon. Silha, revealed to be the ninth strongest adventurer in the world, insists Aao register as an adventurer to earn money. Despite Aao's reluctance and his desire for a NEET life, he is pressured into a B-rank adventurer certification test. During the test, Aao's invincibility proves effective against the branch chief, leading to his unexpected B-rank certification. He also sells the dragon scale, securing funds for his future. Liliria, now his maid, demands wages, further complicating Aao's financial situation. The story ends with Aao contemplating his new life as a B-rank adventurer, still aiming for his ultimate goal of a NEET existence.