With the bandits gone and Rokuko safe once more, Keima decides it's finally time for a break. But his plans to relax are interrupted when a beautiful woman shows up on his doorstep. This woman isn't just anybody, though; she's the Dungeon Core of the imperial city's famous White Labyrinth, Haku! Displeased that her beloved Rokuko is stuck with such a nuisance of a master, Haku challenges Keima to a dungeon battle. The catch? If he loses, he'll be forced to leave and work for her! Will Keima ever be able to catch a break?!