The Labyrinth city of Orario has a massive dungeon at its heart, filled with terrifying beasts. A new adventurer, Bell Crannel, challenges this perilous labyrinth, but not in hopes of finding treasure, but in hopes of picking up a girl.

Bell defeats the minotaur and becomes the fastest adventurer to level up in history. After his success, Bell is given the nickname "Little Rookie." As he sets his sights on the middle floors of the dungeon, Ryuu tells him that if he wants to succeed, he's going to need a bigger party.

After a great struggle, Bell and his party finally reach the 18th floor. Aiz Wallenstein and the Loki Familia are already there, returning from their expedition to the lowest levels of the dungeon. With the danger passed, they enjoy a short break before they head back up to the town.

The Loki Familia are battle-hardened veterans used to fighting monsters. But this opponent is different...

The surface is no longer safe for the Xenos. Now, the Hestia Familia must smuggle them back into the Dungeon. There’s just one problem: The Loki Familia stand in the way.

Bell WILL stay true to his ideals. Even if that means making an enemy of the woman he loves.