18+ Isekai Tensei Dungeon Master: Onsen Dungeon wo Tsukuru

"You have been reincarnated as our Dungeon Master. Lure in many adventurers with their desires, and through exploration and combat, create a dungeon that can drain their blood, magic power, and life, Master."

One day, a man on the verge of death in a hospital in the modern world hears a strange hallucination. It tells him to operate a dungeon as a Dungeon Master. Faced with this unusually specific hallucination, the man, while lost in fantasies of dungeon management, passes away from his illness.

And now, just as the hallucination foretold, the man is truly reincarnated as a Dungeon Master. To the Dungeon Core who had been the source of the hallucination, he declares:

"Alright... I'm going to make a onsen dungeon."

And thus, his dungeon management begins.

(Source: Novel Updates)