Bell and crew stumble into an underground hot spring and immediately the show stops pretending it's anything other than an excuse to draw attractive people wet and half-clothed. The fanservice isn't sneaking around being "tasteful", it's shameless, constant, and exactly what you came for. The hellhound fight that bookends it all has actual animation budget behind it, which makes the whole thing feel less like filler and more like the series saying "we know what you want, here it is, enjoy."

After the crisis on the dungeon's 18th floor, Bell, Hestia, Lilly and their allies start the trip back to the surface, only to stumble into an uncharted area hiding a secret hot spring. What should be a perfect chance to relax quickly becomes complicated when they realize the springs harbor more than just warm water and steam. Hermes happens to have bathing suits ready for all the ladies, each in exactly the right size. The group takes a well-earned break from their hardships, but something lurking in the dark has other plans, and Hestia still has something she has yet to come clean about with Bell. This single OVA mixes adventure, comedy, fantasy, romance and fan service, pairing a relaxing soak with a mystery that turns dangerous.