"Come on, kill all those bandits for me already!" "No thanks. I don't wanna do any work." My name is Keima Masuda, and my hobby is spending each day doing exactly nothing... but one fateful night, I was summoned to another world where I met a blonde young girl who I named Rokuko. It seemed that fortune had favored me and I would soon be living a wonderful life free of work. But even though I'm a guy who loves sleeping more than eating, Rokuko demanded that I help her. "Save my dungeon! By the way, since you're the Dungeon Master, you'll die too if the Dungeon Core is destroyed." The dungeon only had one room, and it was already surrounded by bandits. Seriously? It's a checkmate already. I've gotta break out of this impossible situation so I can stop working and just sleep!...