Dungeon ni Deai wo Motomeru no wa Machigatteiru Darou ka III OVA

Orario has a new natural hot spring thanks to the Dian Cecht Familia, but Naaza of the Miach Familia suspects an elaborate con and needs help to prove it. That means Bell is caught in the middle of an ongoing rivalry between two Familias. Again.
(Source: HIDIVE)