Demon Lord, Retry! (Manga) Volume 4 by Kurone Kanzaki

Hot Springs, Pumping (for Information), and New Allies.
Once the Demon Lord things has things bubbling away at the Hot Springs Resort, it's time to get down to business. In a situation like this, that means adventuring, and what better partners than the sullen Mikan and thirsty Yukikaze? As the trio head north to the city of Rookie, home of the Bastille Dungeon, the Hellions and Anima are on the move in pursuit of their own motives, most likely to the detriment of the humans. Can the resort team stay safe in the Demon Lord's absence?