Prologue

Heya, the name’s Keima Masuda! I’m the Dungeon Master of this here [Cave of Greed]! But keep that a secret from everyone, okay? Dungeon Masters die if their Dungeon Cores get destroyed, and I sure don’t want to die just yet. I just want to sleep and be lazy.

Thus, I need to build an impenetrable dungeon fully capable of protecting the Core. But that takes a lot of DP, or Dungeon Points. You need to lure people into your dungeon to get DP. And that’s exactly what I did. I took the [Ordinary Cave], a single room dungeon infested with bandits, and expanded it in every way to safely attract visitors. While I was at it, I built an inn nearby to squeeze extra DP out of them. I got to sleep there too, of course. Two birds with one stone.

One thing led to another and I ended up getting involved with Haku, my dungeon’s older sister, before accidentally breaking a hole into a neighboring dungeon... A lot happened, and for some reason, a town ended up being built around my inn. I ended up as its town chief and named it Goren Town. It wasn’t really my style, but better that than letting some good-for-nothing force me into working. And of course, I don’t do any of the actual town chief work myself!

A lot happened last winter too. Rin, a real pain in the butt Slime monster taking the form of a black wolf, took over part of my dungeon to hibernate, and on top of that, the High Priestess of the Holy Kingdom came to spread the teachings of the Church of Light, also known as the Church of Fucking Destroy all Dungeons. Well, I somehow managed to survive the both of them.

The High Priestess didn’t leave much behind except the contents of her wallet, but Rin gave us some very useful weapons known as Gravity Bombs. But how strong are they, really? Not strong enough to destroy a whole dungeon, right...? I honestly don’t know where to store them. They said the explosion would be “pretty big” or something, but...

Anyway, yeah. A lot happened and I gotta wonder why. I never intended for the dungeon to get so big, but now there’s a whole town around it with plenty of people. It kind of feels like I’m walking down a road someone paved for me. Where is this road taking me?

...It’s been about a whole year. I’ve gotten tired of counting the days since I was summoned to this world.

Suddenly, someone opened my door without knocking.

“Keima. Do you have a second to talk?” A beautiful young blonde girl walked into my room without an ounce of hesitation. She’s the avatar of the Dungeon Core, or in other words, my partner.

...Let me explain something. As Dungeon Master, I’ll die if the Core of my dungeon gets destroyed. But even if I die, the Core—this girl—will be just fine! Oh, and why am I working as a Dungeon Master at all if that’s the case? ’Cause she summoned me. Me. As a monster. She summoned me as a monster. Through a gacha system, even. Some god or whatever talked to me on the way here and asked me to be a Hero, but those Heroes mainly just destroy Dungeon Cores. They’re called Soldiers of God by the dungeons themselves. But I’m a Dungeon Master. Hahaha! As if I’d do all that. I just wanna sleep, anyway.

...Oh, right. Some Heroes did eventually come to our dungeon. I survived one... or rather, ripped him off and stole his money... and beat back the other... or rather, stuck him into a solid stone wall to live in partially suspended animation with full consciousness for the rest of his potentially eternal life. Given how I’m working as town chief just fine now, well, you could say it all ended well. I was fine as long as I could sleep peacefully. Just no eternal sleep, please.

I turned to look at Rokuko.

“So? What’s up?”

“I wanted to ask about the dungeon. You built a lot of stuff while that annoying slime dog was hibernating here, right?”

“Ahhh, yeah, I made some big changes. Mainly deep inside the dungeon.” Our dungeon started with a simple entrance complete with normal Goblins. After that was a labyrinth, then a Puzzle Area (mostly destroyed by Rin), then a spiral staircase, then a storeroom area which split into four branches. One was the magma area which Rokuko built, leading into the neighboring [Flame Caverns]. One was the plains area, which I built because I wanted to see what the dungeon’s weather/atmosphere function looked like (the plains looked endless, but had invisible walls which would block progress). One was the coliseum area behind the original Core Room. And finally, one was the (half-finished) new Puzzle Area which I had built from the wreckage of the old Puzzle Area.

However, over the winter, I finished the new Puzzle Area, and built a second Core Room behind it. The other Core Room had a Dummy Core. This new Core Room at the bottom of our dungeon had two layers, with the main room having a Dummy Core and the hidden room having another Dummy Core. Why did I do something that seemingly pointless? Well, because I honestly didn’t know where to put the real Core.

There were skills such as the High Priestess’s {Treaty} that could prevent moving the Dungeon Core effectively, so I wanted to keep it in the safest place possible. But even with that in mind, it wasn’t smart to just put the Dungeon Core in the deepest place possible. The adventurers of this world already know that there’s a strong tendency for Dungeon Cores to be at the bottom of a dungeon. That’s why I initially built the hidden layer of the room, to keep the real Dungeon Core... but changed my mind after considering the real possibility that someone might see through the trick.

In the end, I decided to hide the real Dungeon Core in one of the coliseum area’s light fixtures. The Core was, ultimately, just a shiny ball on the outside. The best place to hide a shiny ball is in the middle of a bunch of Light magic tools—that is, equally shiny balls. It seems kinda risky, but eh, it’ll be fine for now. I’ll need to make some changes if someone capable of smashing through the new puzzle area comes around, though.

“Uh-huh, uh-huh. Our dungeon’s a lot stronger now, huh? Ah... Right, Keima. I’m going to be leaving the dungeon for a bit, is that okay?”

“Leaving the dungeon? Uh, sure... Where are you going?” I had no idea where she might be wanting to go. Maybe she had some business in Tsia or Pavella?

“The yearly gathering of dungeon cores is coming up.” Oh yeah... I remember her mentioning that at some point.

“You don’t need me to come with you?”

“Mmmm. I’ve never seen anyone bring their Master with them. I don’t think you can come. Don’t worry, I’ll be back in two or three days, probably. I couldn’t go last year because of the bandits.” So basically, not much will be different.

“Alright. So, when is it?”

“Oh, um, today.” Rokuko’s body began to shine gently.

“Er, is that...”

“Uh-huh. I’ve gotta go now, bye bye. Not that I really want to.” A magic circle briefly enveloped Rokuko, and then, with a pop, she was gone.

“Wait, by today you meant right freakin’ now?!” C’mon, don’t wait until literally the last second to tell me.