The narrative follows Kazuma Kagotsuru, a high school student who, disillusioned with societal competition, had stopped attending school. His life takes a dramatic turn when his entire first-year class is summoned to the fantasy world of Aristea by the kingdom of Glust, which is under siege by demons. Kazuma, despite being a recluse and not physically present at the summoning circle, is inadvertently transported due to his enrollment in the class.
In a surreal encounter, Kazuma meets the god of Aristea, who explains the summoning and offers him a "gift" as compensation for the imperfect transfer. This god possesses the ability of "Probability Manipulation," which he demonstrates by ensuring both he and Kazuma have tea with a tea stalk. Kazuma is presented with a list of potential gifts, but many of the powerful ones, such as "Hero," "King of Swords," and "Sage," are already taken by his classmates, including Kazuma Hijirikawa, the designated "Hero." Kazuma, prioritizing his reclusive nature, chooses the hidden gift "Home," which creates a pocket dimension resembling his house.
Upon arriving in Aristea, Kazuma finds himself in his home, albeit in a dark, unknown space. He discovers that his "Home" gift allows him to live comfortably with access to food and utilities, though without internet. He also learns that using household items consumes MP, but this process also grants him experience in various magic skills, including multiple elemental affinities and Spatial Magic. He experiments with his abilities, realizing that while magic is unusable within his "Home," using appliances and the gift itself levels up his skills. He also gains the "Refresh" ability, allowing him to restore used items to their original state, effectively granting him an infinite supply of food and the ability to repair his "Home."
Meanwhile, Kazuma's classmates, led by the exceptionally talented Kazuma Hijirikawa, are welcomed as heroes by Princess Misha of Glust. They are impressed by their "Status Open" ability and their gifted powers, readily agreeing to fight the Demon Lord. However, not all classmates are enthusiastic. Akira Mitsugawa, a delinquent and Kazuma's friend, is skeptical of the kingdom's motives. Mikku Arisugawa, who harbors feelings for Kazuma, is distraught upon discovering a blood-stained pajama, believing Kazuma to be dead due to the summoning's side effects. She resolves to find him and heal him with her "Saintess" gift.
Kazuma, after a month of training and leveling up his "Home" and magic skills, ventures out of his sanctuary. He encounters an Orc, which he easily defeats with his powerful lightning magic, "Gungnir," inadvertently causing significant environmental damage. Following the path of destruction, he discovers a road and eventually the capital city of Glust, Grisnia. He enters the city disguised as an adventurer from a remote village, receiving assistance from a kind guard named Bans. At the Adventurer's Guild, he registers as an F-rank adventurer, his unusual abilities and the large quantity of monster materials he presents raising eyebrows. He learns that his classmates are already involved in the kingdom's war efforts and that the current king and princess are unpopular, hinting at potential political machinations behind the summoning. Kazuma, now a capable adventurer with unique abilities, decides to gather more information and potentially reunite with his classmates, all while keeping his true power and his "Home" gift a secret.
