Is it wrong to try to pick up girls in a dungeon?

"Thanks to Aiz and crew, the tumultuous events of Monsterphilia ended without incident, and Loki Familia is finally able to relax--but only for a moment. Soon, they find themselves embroiled in a suspicious case of murder. As they begin to investigate, the ladies soon realize that they're getting involved with a killer that's more horrifying than they thought... In the midst of all this, they find a mysterious jewel that may connect to everything else. These events taking place above and below the surface will rock Orario to its core as the darkness lurking in the city bursts forth!"--Back cover.