The story begins with Sanada Nobuyuki, a 25-year-old unemployed man, realizing he has died in a car accident and found himself in a pure white, empty space. Overwhelmed with despair, he eventually calms down and is greeted by two gods, Sophitia and Asterio, who manage the world of Permuridias. They reveal their intention to reincarnate Nobuyuki into their world, a request that initially leaves him confused and hesitant.
Sophitia explains that 100 years prior, their inexperience as new gods led to the catastrophic collision of two worlds: Permus, a realm of magic inhabited by elves, beastmen, demons, and dragons, and Lidia, a science-based world populated solely by humans (Nobuyuki's original world). The collision nearly destroyed both, forcing them to merge into Permuridias. Most souls of the deceased were scattered into other worlds, and Nobuyuki is one such "lost soul" they are tasked with retrieving as part of a divine trial to restore their beloved world. Moved by their sincerity and love for Permuridias, Nobuyuki accepts the offer, requesting to keep his name and have his existence erased from his former world. The gods grant him "skills" as a blessing before he loses consciousness.
Nobuyuki awakens as a child in a small hut, quickly realizing he has been reborn and physically regressed. He is found by Zegil, a kind, one-armed old man who took him in. Nobuyuki struggles to explain his origins, leading Zegil to initially view him with pity due to his profound lack of basic world knowledge. Zegil, a former adventurer, eventually takes Nobuyuki to the graves of his deceased party members, Gengo and Rachel. Seeing a resemblance in Nobuyuki's naivety to his late friend Gengo, Zegil feels a sense of destiny and offers Nobuyuki a home, which the boy tearfully accepts, calling Zegil "Grandpa."
Two years pass, and Nobuyuki, now around 10 years old, has been diligently tutored by Zegil in Permuridias' history, geography, races, currency, and combat. A significant discovery is that humans cannot use magic, a limitation stemming from their Lidian origins where magic didn't exist. Instead, humans possess unique "skills." Nobuyuki learns he possesses a rare "Unique Skill: Limit Break," which removes his physical limits. This, combined with his choice of the katana (Zegil's former weapon), ignites Zegil's passion for teaching, leading to incredibly intense, often dangerous, mock battles.
During one such training session, Nobuyuki awakens two new sword skills. To celebrate, Zegil takes him to Lyusion, the bustling central city built to guard a dungeon. Nobuyuki is awestruck by the city and learns more about the world's history, including the "Void God" that forced all races to unite after the collision. In Lyusion, he receives his first custom-made katana from Jesta, a dwarf blacksmith, which perfectly suits him. They then stay at the "Badger's Den" inn, run by Zegil's friends, the beastmen Garam and Anna, and meet their daughter, Cashel, who is Nobuyuki's age. Nobuyuki's journey from a lost soul to a determined swordsman with a new family and purpose has begun.
