The story begins with the protagonist, a 38-year-old factory worker named Erik, lamenting his monotonous and unfulfilling life. He works long hours, has little social life, and feels his youth has passed him by. One evening, while buying alcohol, he witnesses a group of cheerful college students and feels a pang of envy for their seemingly vibrant lives. Suddenly, a sports car veers out of control, heading directly for the students. In a moment of selfless instinct, Erik shoves them out of the way, sacrificing himself and losing consciousness.
Erik awakens in a grand, church-like hall filled with awestruck young people. He is addressed as "Erik" by a kind old priest named Cliff. Erik realizes he has retained his memories from his previous life, a common trope from the light novels he used to read, and understands he has been reincarnated into a new world. He is participating in a "Blessing Ceremony," a ritual where 15-year-olds receive a divine gift that will shape their future. Erik, having experienced an unprecedented radiant glow during the ceremony, is eager to discover his blessing, hoping for something powerful like "Sacred Sword Skill" or "Great Magic," or at least a specialized skill like "Healing Magic" or "Water Magic." He dreads receiving a low-tier blessing like "Fire Magic" or "Land Development," which would lead to a life of hardship.
His blessing is revealed to be "Room," a spatial ability that creates a pocket dimension. While initially disappointed by its seemingly limited capacity compared to others' blessings like "Item Box," Erik soon discovers its true potential. He is joined by his childhood friends, Rex, a budding warrior, and Miranda, a mage, along with a priestess named Serene, who acts as their instructor. They are training in a low-level dungeon, a common practice for those who have received blessings, preparing them for formal schooling and future careers.
During their dungeon exploration, Erik uses his "Room" to store monster cores, a task that usually requires carrying them. He also uses it to hide from a large, dangerous creature. He realizes that his "Room" can expand by absorbing monster cores. This ability proves invaluable when a "Pandora Switch" accidentally activates a hidden portal, transporting Erik to a dangerous "Dual Dungeon" filled with magma.
Trapped alone, Erik uses his "Room" to survive, hiding from powerful monsters. He discovers that the "Room" not only expands but can also accommodate living beings. He also finds a red stone, the "Dungeon Core," which he takes. Using the "Room" and the "Dungeon Core," Erik manages to escape the Dual Dungeon and return to the surface, where he is reunited with his worried friends and father.
Back in town, Erik is questioned by the Adventurer's Guild. He reveals his escape method, and his "Room" is examined, revealing its immense size, capable of holding a mansion. The Guild Masters and Sub-Master are astonished, classifying his blessing as a rare "Special Type." They are particularly interested in the "Dungeon Core" he possesses.
Later, while resting, Erik hears a voice within his "Room." He discovers it belongs to a sentient entity named "Eve," the administrator of "The World," a space created by his ability. Eve, who absorbed the "Dungeon Core" and the monster cores, explains that she can communicate directly with his mind and that her purpose is to protect him. Erik, overwhelmed by these revelations, asks Eve to teach him about his newfound abilities.
