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.

At Bell's urging, Hestia reluctantly lets Lili into the party. Bell, worried about his weakness as he continues to go deeper into the dungeons, accepts an offer of help from Aiz Wallenstein, the girl he loves.

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.

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