Before I realized, I had become the guardian of a dungeon, a Demon Lord. I was suddenly in a dangerous world with giant monsters loitering around, fighting for their existence, so I thought to go about developing the dungeon in order to not die but —- for some reason I was having quite the good time…. How did it turn out like this?... more>>

The protagonist, Yuki, having to live in that world now, uses his bold and sharp senses and spends time with a supreme dragon girl and a vampire girl; Sometimes laughing, sometimes being angry, passing days doing what he likes.

(Source: novelupdates) <<less

Masuda Keima, a lazy high-school boy who prefers to laze around and avoid working, gets summoned as a dungeon monster by a girl avatar named "Dungeon Core No. 695" who is the dungeon core of the mighty one-room dungeon "Ordinary Cave".... more>>

Through a mishap she accidentally assigns him as her Dungeon Master, so first order of business is to get rid of those pesky bandit invaders that have set up camp near the heat-emitting dungeon core before they get the idea to smash it and kill them both. <<less

Akira the Dungeon Master: From Weakest to Strongest! Reborn in another world as a dungeon master, Akira Hanamura constructs a cozy dungeon within just 30... more>> minutes. However, there's one major flaw—this "perfect" dungeon has zero defenses against the flood of adventurers seeking its treasures. It’s a ticking time bomb where being conquered means instant death for Akira. In this desperate situation, Akira discovers the potential of his unique 《Reproduction》 skill. To survive, he must expand his forces by creating new monsters, utilizing both female adventurers and monster girls as vessels to grow his dungeon's strength. What starts as the weakest dungeon turns into a relentless rise to power as Akira battles to create the ultimate stronghold. An erotic and high-stakes dungeon-building fantasy born from Nocturne Novels—prepare for a thrilling journey of strategy, survival, and unexpected alliances! <<less