Ryu Han-bin has just been discharged from his mandatory military service in South Korea when a mysterious entity kidnaps him and transports him to another world. He is sent to Selha Latna, an artificial and hostile training dimension meant to prepare otherworlders like himself for the main continent of Rathna by having them level up using a Guideline, a game-like system. However, a critical error in Han-bin’s Guideline prevents him from advancing beyond a low level. This glitch traps him alone in the tutorial zone for over twenty-two years, forcing him to battle increasingly powerful monsters repeatedly. Each time his experience points would allow him to level up, the broken system resets him back to level one, creating a grueling cycle of survival with no progress in sight.

After two decades of this forced solitude and relentless combat, Han-bin is finally released into the world of Rathna. While his official level remains deceptively low due to the glitch, the immense practical strength, combat experience, and physical abilities he gained during his endless tutorial have made him overwhelmingly powerful, operating on a completely different scale from normal otherworlders. Upon arrival, he quickly discovers that Rathna is a vast fantasy world where otherworlders from Earth, known as Aliens, are widely despised. The continent is governed by a pantheon of Goddesses and their powerful mortal servants, the Templar Lords, but a deeper conflict brews involving the evil god Ormphlaus, who is revealed to be the creator of the Guideline systems.

As Han-bin ventures through Rathna, seeking only to survive and perhaps find a way home, he forms a party of powerful companions. He is joined by Atisse, a young dragon who can take human form, and Ephyr, a wyvern with the same ability. Together, they navigate a world that views them with suspicion and hostility. What begins as a personal struggle for survival quickly escalates into a much larger mission to confront Ormphlaus, who seeks to conquer Rathna, forcing Han-bin to use the deceptive strength hidden behind his low level to protect his new home and allies.

A notable aspect of the narrative is the significant divergence between the original web novel and the manhwa adaptation, with the webtoon altering character personalities, past histories, and entire storylines, effectively becoming a different interpretation of the same premise. The story is structured across multiple seasons, following Han-bin as he registers with a hunter's guild, uncovers the truth about the Goddesses, and engages in a desperate struggle against the divine forces manipulating the world, all while coming to terms with his own disorienting power and fractured past.