Dungeon ni Deai wo Motomeru no wa Machigatteiru Darou ka OVA / ダンジョンに出会いを求めるのは間違っているだろうか OVA「ダンジョンに温泉を求めるのは 間違っているだろうか」

Following the crisis on the dungeon's 18th floor, Bell Cranel and his allies head back to the surface. However, their journey is delayed midway when the group stumbles across uncharted territory that hides a pleasant surprise—a hot spring! The group takes a respite from all the hardships they have endured. Unfortunately, as everyone relaxes in the bath, they discover that the hot spring may hide an evil secret. ...