The Labyrinth City Orario possesses the only underground labyrinth, or better, dungeon, in the whole lower world, and thus has prospered from it, coming to be known as the "Center of the World". In this city, a certain Ryuu Lion has worked under Mia Grand at the pub "Hostess of Fertility" alongside her coworkers Syr Flova, Arnya Fromel, Chloe Rollo, and Lunoire Faust.

One day, a certain incident at the pub changes the pace of things, inevitably shattering the peace and atmosphere, and things will never be the same for Ryuu as a chase begins for an innocent girl caught in events beyond her control...