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.

For an adventurer to level up, and truly get stronger, he has to go on an adventure. Bell travels down to the lowest of the upper floors of the dungeon, where he encounters a minotaur with a giant sword. Lili is badly injured, and Bell is unable to leave her behind. Aiz arrives again to save him, but he waves her off...

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.

A massive floor boss has crashed down from the upper floors and begun tearing apart the adventurers. Aiz has left for the surface, and it's up to Bell and his friends to defeat the monster. With their escape route cut off, it's do or die if they ever want to see the light of the sun again.

A massive floor boss falls from above and traps the adventurers. The only way out is up, and to get back home Bell will have to defeat it without Aiz's help.

Apollo Familia has laid down their challenge, but Hestia refuses. Apollo tries to force her hand...

It's time for the War Games, and the Hestia Family, and its new members, are ready. Can they defeat the entire Apollo Familia and save Bell from Apollo's clutches?

Never underestimate the measures a fanatic will take to prove his worldview correct.

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.

As Hermes finally reveals his true intentions, Bell battles the most powerful opponent he's ever faced.