This is a world decades after the Demon King was defeated. Guest sets out on a journey aiming for the title of the world's strongest, the [Overlord]. Along the way, Guest meets Ram, who just happens to be looking for an apprentice.

Rank System In this world, adventurers are divided into six ranks from S to E. S-Rank: Granted the right to descend below the 50th floor of the dungeon alone. Possesses enough power to destroy an entire city. A-Rank: Granted the right to freely go up to the 50th floor alone. B-Rank: Granted the right to freely go up to the 40th floor alone. Can go up to the 50th floor if in a party. C-Rank: Granted the right to freely go up to the 30th floor alone. Can go up to the 40th floor if in a party. D-Rank: Granted the right to freely go up to the 20th floor alone. Can go up to the 30th floor if in a party. Most adventurers belong here. E-Rank: Granted the right to freely go up to the 10th floor alone. Can go up to the 20th floor if in a party. The weakest level in this world. Finally, the title of Overlord is bestowed upon those within S-Rank who are exceptionally strong and possess the power to rival a Demon King.

There are dungeons in this world. The highest floor ever reached is the 83rd. As the floors get deeper, the monsters become stronger. They don't just get stronger; their intelligence also increases.

For low-rank adventurers to dive into deeper floors, they must form a party. A party is officially recognized with a minimum of four members: a Warrior, a Healer, a Mage, and an Assassin.