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.

It is business as usual in the massive city of Orario, where legions of adventurers gather to explore the monster-infested "Dungeon." Among them is the easily flustered yet brave Bell Cranel, the sole member of the Hestia Familia. With the help of his demi-human supporter Liliruca Arde and competent blacksmith Welf Crozzo, Bell has earned the title of Little Rookie by becoming Orario's fastest-growing adventurer thanks to his endeavors within the deeper levels of the Dungeon. This season continues Bell's adventures as he tries to bring glory to his goddess and protect those he cares about. However, various familias and gods across the city begin to take notice of his achievements and attempt to add him to their ranks.

Upon his run-in with a Vouivre—a monster known to be very dangerous—Hestia Familia's captain Bell Cranel is struck with incomprehension. Despite its preceding reputation, the supposed bloodthirsty creature happens to be crying and flees from a group of adventurers. The monster, taking the form of a terrified little girl, prompts Bell to swiftly decide to hide her. Unbeknownst to him, this act of kindness will cause massive repercussions that will soon echo throughout the entire city of Orario.

Intrepid adventurer Bell Cranel has leveled up, but he can’t rest on his dungeoneering laurels just yet. The Hestia Familia still has a long way to go before it can stand toe-to-toe with the other Familias of Orario — but before Bell can set out on his next mission, reports of a brutal murder rock the adventuring community! One of Bell’s trusted allies stands accused of the horrible crime, and it’s up to Bell and his friends to clear their name and uncover a nefarious plot brewing in the dungeon’s dark depths.

As the labyrinth city of Orario prepares for the Goddess Festival, Bell Cranel looks forward to the festivities after his and Ryu's harrowing escape from the Dungeon's darkened depths. However, in a small tavern tucked away on a street corner, the single decision of a young woman causes a chain of events that throws Bell's life and the entire city into chaos.