Dungeons.

They are magical spaces able to create something out of desire. It was quantified as Dungeon Points (DP).

With the Dungeon Core, you can use your DP to get anything you want. From bread, furniture, video games--even futanari sex demons.

This world used to be relatively peaceful. We went to school and work like usual, until the Demon King revived, with strength powerful enough to destroy the world.

He sold dungeon cores to the highest bidder, and normal humans were able to become dungeon masters. The one benefitting the most were the richest people.

Many jobs were lost.

Dungeons were able to summon loyal creatures that would take care of menial labor without complaint.

The remaining people who still had a job consist of creative workers, researchers and so, who could create modern stuff. Even so, most of their activities were inside a dungeon.

The Dungeon Cores from the Demon King could give birth to lower-tiered ones, and did so recursively until it came to the lowest tier.

More and more places became dungeons.

You can become a dungeon master, as long as you can afford the lowest tiered core.

The cores were always sold out the moment it's online. Territories started to overlap with one another and Dungeon Wars exploded everywhere.

It was the Age of Chaos.

Working is no longer necessary. We can live inside a dungeon and contribute to our DP to the landlord, which is the Dungeon Master. As long we contribute enough DP by living to the fullest, we can do anything within the limits.

If we're not a dungeon resident, there'd be people forcing us to become a part of it. It's a matter of luck, to find a good landlord, and hope their dungeon would last a long time.

There was no longer any need for water, electricity, and internet connection. Everything's covered by dungeons.

If we want to travel abroad, there's a teleportation formation that could bring us several thousand miles.

As a riskier alternative, those living outside a dungeon could spend their time at a nearby dungeon, that's designed to rouse desires. Something like an Internet House, Manga Cafe, Brothel, or so.

Most who did so, 'cuz they're still deciding which landlord we should go to, but I wouldn't count on them. There's no free lunch, these part-time landlords would bug you to hell 'bout joining in.

That's why we had been holding my best with what we have. Me and my lil' sis.

Especially the moment a dungeon consumes another core, it would be strengthened. The higher the tier, the more you can do with it. The stronger and more extensive the summoned things will be.

There were other ways for Dungeon Cores to evolve, but I hadn't heard anything 'bout it.

Anyway--even if the Dungeon Master killed, as long the Dungeon Core remains intact, they would live forever.

A lot wanted to become stronger. Living in fear, of others taking their belongings.

For some reason, only Humans could generate DP. While Demons only produce them when they're killed.

The stronger your desires, the higher DP you could produce. Not to mention, some landlords would treat fellow humans terribly to produce more DP.

I was really afraid, of what's going to come next.

Not having the power to decide for me, was terrifying.

In a way, the Demon King had enslaved humanity in one fell swoop.

==

For the longest time, I and my little sister tried to get our hands on a dungeon core.

We didn't like the thought of living under someone else, but it's even harder to become a Dungeon Master.

Our parents went missing right after the Demon King's arrival and life was tough with what little we have. Thinking 'bout it, what miracle it was, to survive so far with no background.

Alas, Fate hadn't abandoned us.

When I was cleaning the basement one day. I noticed a floor tile was out, and there seems to be an entrance leading beneath.

Peeking down, the interior was something ancient; it resembled a medieval castle. One thing I noticed was a large altar, and a gigantic circular crystal, giving a mystical glow.

It's drawing me in. I couldn't help to climb the altar and touch the giant crystal ball.

There's a series of messages in front of me.

I immediately came to my sister, who's currently preparing breakfast.

I thought she'd be delighted, but colors left her face and she almost fell down.

"No...Onii-chan..."

"What's wrong? Aren't you the one most adamant to get a Dungeon Core?"

"Why do you activate this first without telling me! Being a Dungeon Master is a huge responsibility, especially since it'll attract tons of hungry wolves. Someone reckless like you..."

"Actually, lil' sis—do you believe a Dungeon Core that chooses its master?"

"I've heard of it."

"It was drawing me in, like its directly calling for me. I will make the best use of its power, to respond to its trust."

"Don't try to keep me out of this, Onii-chan. No matter what, I'll give my all to help."

"Sigh..."

"W-what was that for? I'm not a weak little girl who you should protect at all times. I too, want to get stronger."

In the end, I just can't win against her resolve.

"Very well, how about being my [Overseer]?"

"Alright, Boss!"

She made a military salute while donning her blanket as a cape.

"Lil' sis, this is not a game. One mistake and we'll be dead, are you sure you're up to it?"

"Much better than let you take charge of everything."

I noticed one thing 'bout the dungeon core. Despite its prowess, no one could feel its presence. Otherwise, my lil' sis who possesses strong spiritual energy would detect it long ago.

We had a ton of DP, but the only 'dungeonized' place was the core room. Although, our house also considered to be a part of it.

Despite its concealment ability--what if someone could sense the core? What if we're not strong enough to defend?

How do we design an ideal dungeon, in such a cramped place?

"Onii-chan, what kind of features did the core have?"

"It can build things and expand. It also has information gathering."

Tapping on the screen a few times, our location wasn't that bad. There were several small dungeons, like the internet house and apartments. Our residential district had mostly vacant homes.

There's also information about the Dungeon Masters. It's something you can get while searching the internet.

My lil' sis was deep in thought before she raised her finger.

"None of them seem to be an ambitious bunch. It's troubling since we couldn't see any news 'bout dungeon battles. What 'bout the history...ah!"

Lil' sis rapidly tapped on the screen and found several tabs.

"Mr. A from Fujisaki Hostels...they're expanding at an alarming rate. We should be careful. They're targetting the residential areas near us."

"Is it a medium-class dungeon?"

"No...a large-class, but they shouldn't use a lot of force. Onii-chan, what class is our core?"

"It doesn't show anything, but there are lots of strong-looking baddies in here."

"What? Onii-chan let me see!"

==

One month later...at Demon King's Castle.

An old man with thick horns and tanned skin held a newspaper, with a cigar in his mouth.

[A new Demon King has awakened in Saitama.]

The building gave the impression of a futuristic stronghold, with cyborgs wielding laser rifles, anti-matter cannons, and mechas.

The Demon King dropped his cigar when he read a certain line.

[The place is also selling a new, full dive VR capsule."

...and he dropped his cigar and shouted on top of his lungs, causing the entire dungeon to rumble.

"SEBAS! Buy ONE for each of us, RIGHT NOW!"

This marked the short age of Dungeons.

...and the beginning of the Video Game era.