The final hour of the popular virtual reality game Yggdrasil has come. However, Momonga, a powerful wizard and master of the dark guild Ainz Ooal Gown, decides to spend his last few moments in the game as the servers begin to shut down. To his surprise, despite the clock having struck midnight, Momonga is still fully conscious as his character and, moreover, the non-player characters appear to have developed personalities of their own! Confronted with this abnormal situation, Momonga commands his loyal servants to help him investigate and take control of this new world, with the hopes of figuring out what has caused this development and if there may be others in the same predicament.

Life in the bustling city of Orario is never dull, especially for Bell Cranel, a naïve young man who hopes to become the greatest adventurer in the land. After a chance encounter with the lonely goddess, Hestia, his dreams become a little closer to reality. With her support, Bell embarks on a fantastic quest as he ventures deep within the city's monster-filled catacombs, known only as the Dungeon. Death lurks around every corner in the cavernous depths of this terrifying labyrinth, and a mysterious power moves amidst the shadows. Even on the surface, survival is a hard-earned privilege. Indeed, nothing is ever certain in a world where gods and humans live and work together, especially when they often struggle to get along. One thing is for sure, though: a myriad of blunders, triumphs and friendships awaits the dauntlessly optimistic protagonist of this herculean tale.

Thirty-seven-year-old Satoru Mikami is a typical corporate worker, who is perfectly content with his monotonous lifestyle in Tokyo, other than failing to nail down a girlfriend even once throughout his life. In the midst of a casual encounter with his colleague, he falls victim to a random assailant on the streets and is stabbed. However, while succumbing to his injuries, a peculiar voice echoes in his mind, and recites a bunch of commands which the dying man cannot make sense of. When Satoru regains consciousness, he discovers that he has reincarnated as a goop of slime in an unfamiliar realm. In doing so, he acquires newfound skills—notably, the power to devour anything and mimic its appearance and abilities. He then stumbles upon the sealed Catastrophe-level monster Storm Dragon Veldora who had been sealed away for the past 300 years for devastating a town to ashes. Sympathetic to his predicament, Satoru befriends him, promising to assist in destroying the seal. In return, Veldora bestows upon him the name Rimuru Tempest to grant him divine protection. Now, liberated from the mundanities of his past life, Rimuru embarks on a fresh journey with a distinct goal in mind. As he grows accustomed to his new physique, his gooey antics ripple throughout the world, gradually altering his fate.

Goblins are known for their ferocity, cunning, and rapid reproduction, but their reputation as the lowliest of monsters causes their threat to be overlooked. Raiding rural civilizations to kidnap females of other species for breeding, these vile creatures are free to continue their onslaught as adventurers turn a blind eye in favor of more rewarding assignments with larger bounties. To commemorate her first day as a Porcelain-ranked adventurer, the 15-year-old Priestess joins a band of young, enthusiastic rookies to investigate a tribe of goblins responsible for the disappearance of several village women. Unprepared and inexperienced, the group soon faces its inevitable demise from an ambush while exploring a cave. With no one else left standing, the terrified Priestess accepts her fate—until the Goblin Slayer unexpectedly appears to not only rescue her with little effort, but destroy the entire goblin nest. As a holder of the prestigious Silver rank, the Goblin Slayer allows her to accompany him as he assists the Adventurer's Guild in all goblin-related matters. Together with the Priestess, High Elf, Dwarf, and Lizardman, the armored warrior will not rest until every single goblin in the frontier lands has been eradicated for good.