Astrea Record: Dungeon ni Deai wo Motomeru no wa Machigatteiru Darou ka - Eiyuutan

Seven years before a certain boy will arrive in the Labyrinth City, an era of chaos and strife reigns supreme. Ryu Leon spends her days serving the goddess Astrea while searching for a brand of justice she can believe in. She's not alone, for the rest of Astrea Familia are a rare source of light in these dark times. In the shadows, however, something evil is stirring—a threat that will shake Orario to its very foundations…!

(Source: Yen Press)