Emerging from 250 Years of Seclusion

Now that I'd come out, there was one thing I had to explain before moving on. I hate dying. Even a thin, thread-like long life is better than the alternative. That's why, personally, I respect guys like demon kings the most. They're fated to get beaten to death by the hero, but they don't even look back, they just go ahead and cause chaos. That's no ordinary courage.

But that didn't mean I wanted to become one myself. I got possessed into a certain mainstream novel. A story where the hero grows strong, defeats the demon king, and becomes a legend. And I possessed the demon king in that novel, the wicked one. A beautiful woman with black hair and black diamond-like eyes. The demon king being female was a traditional cliché that had led to this mess.

When I first possessed her, I felt a deep sense of regret. Getting stabbed by the hero was the predetermined route? No way in hell. After agonizing over it for a bit, I made my decision. Run away.

If I just bailed, the demons would collapse easily anyway. What about the remaining demons? According to the setting, demons were puppets created by the demon king, they had no ego. If demons had any sense of life, I'd try to make peace with the humans as much as possible... but since they didn't, there was no need to feel responsible.

And so, on the second day after possession, I packed my bags and bolted like hell. To the deepest part of the Demon Realm. Into an infinite darkness where not even dust could find its way.

I planned to lay low here until the world quieted down. Occasionally, I'd order other demons to bring me necessities, but after about a century, even those who obeyed vanished. The humans must have slaughtered all the demons once their central pillar—me—disappeared. Good sign.

If more time passed here, people would remember demons as mere historical scraps. And you're probably wondering how I endured this long stretch. The demon king's mental strength was overwhelmingly superior, sure, but mostly it was thanks to training. I spent the time honing my magic. I'm probably several times stronger now than when I first arrived.

Then why not remake the demons and invade the human world? I was never interested in world conquest. If power mattered to me, I'd have jumped into politics before possession. Besides, just training in seclusion started to feel comfortable—like holing up in my room playing games nonstop. It was oddly satisfying. Train, lie down, train, lie down... Time flew by like that. I stopped counting after 250 years. At this point, demons were surely just historical footnotes. Time to head out.

I looked like a beautiful woman anyway, so no one would suspect me of being a demon. Thud, thud. I stepped out of the darkness for the first time in ages. Nothing around—just like before I entered. But as I ventured further, the state of the Demon Realm hit me all at once.

The once-majestic demon king's castle was mostly rubble, clinging to faint traces of its former glory. Bloodstains and human gear littered the ground—probably from the dead. Time and ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠the environment had rotted even the bones away. I sighed deeply at the devastation and kept walking.

Near the ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠Demon Realm's entrance, there's a passage connecting to the human world. I could check the outside from there and slip out—no problem. Gotta be careful, though; the entrance might've been preserved as a cultural relic.

But...

Huh?

Where'd it go? I scanned around the entrance area, but there wasn't even a trace of the passage. What? Why's it gone? Did the humans seal it?

No, that doesn't fit...

Per the setting, humans' magical level wasn't high enough to close the Demon Realm's entrance. If it were possible, they'd have done it before the war. So maybe magic advanced and they sealed it later?

Possible, but...

No big deal. Zzzt. The entrance was opened by the demon king in the first place. Think a way stronger version of her—like me now—couldn't reopen it? I pried space open with my fingers and tore it forcibly. Beyond it, the human world appeared.

Whoa, what the fuck?

Why does this feel so familiar?

This body had freakishly good memory. Centuries-old memories were still intact. Even pre-possession ones. This scenery... it was definitely etched in my mind.

That's... the modern world? It was supposed to be medieval fantasy, why the hell is it modern? Was it not a standard novel but a hunter story? Did the entrance vanish because gates got closed?

No way...

A plausible hypothesis hit me. I'd hidden for way too long. In that time, humans kept advancing, and eventually... reached modern civilization.

Dizzying.

Should I be happy about this?

Yeah, let's be.

Modern civilization meant tons of stuff to enjoy, right? Demons were history by now anyway, so I could just bask in the progress. A bit disorienting, but ultimately a huge win.

Swoosh. I popped out of some alley and sealed the entrance behind me. Stepping onto the street, towering buildings and clear skies filled my view. Like coming home. Wait, it is home.

"Sniiiiif."

I closed my eyes and inhaled deeply.

"Urk!? *Cough, cough*!"

And hacked violently. Seoul's air was worse than the Demon Realm's.

"Huuuuh..."

The Demon Realm's darkness was so pristine, not even dust intruded—the air was clean. After centuries of that, Seoul's smog hit like a nightmare. Now I was wandering the streets.

I'd been thrilled about modern society at first, but then problems cropped up.

Identity.

Advanced tech meant strict identity verification. In the old days, faking an ID was ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠easy. Now everything was in databases—not simple. I was basically an illegal immigrant. One report, and it'd be "Where's your country from?!" followed by arrest.

But more than that.

Walking the streets, something felt off. All life has mana. No bloodless person exists, no mana-less either. Talent divides by amount and control. Using mana naturally increases it.

So why does everyone here have the same pitiful amount?

Knights, mages, even adventurers know how to handle mana—way more than civilians. But these people? Laughably low. If handlers have 100, these folks were 5-10. Meaning no one here could wield mana. Not one, despite passing thousands.

Does that even make sense?

Even old-era civilians had around 20 from casual use. All these people unable to touch mana? Like someone sliced the "mana" concept out. And those billboards, smartphones—no mana at all. Pure science and tech.

Science booming in a magic world? When magic's the easy path? Something was wrong. I needed to investigate...

-Whoa...

-Cosplay?

"..."

Later. I dodged their stares and bolted.

First, clothes.

My current outfit: a luxurious black dress fit for a noble lady. With my looks, it drew eyes like crazy. I ducked into an alley, teleported to a remote rural spot.

How'd I know it was remote? Felt like home. Born in the countryside, moved to Seoul. But...

Definitely not my original world.

Everything differed from my hometown. Beyond remote—practically deserted. The kind of backwater outsiders tread carefully. Ours ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠wasn't like that. I wandered, scouting.

No one around. Houses dilapidated. Infrastructure outdated. Real deal countryside. Deeper in, homes looked barely habitable. By the end, abandoned ruins everywhere.

Hm?

One ruin pulsed with dark energy. Demonic energy. The corrupt power of evil beings. I used it too. But why here...?

Curious, I approached the ruin.

A person?

Inside, someone lay face-down, sleeping. Oddly, skin pitch-black.

No, weird way to put it.

Not racist—literally unnaturally black. Like a rotten banana, not natural ebony. Frowning, I crept closer.

Then.

Screeeeech.

The figure's head spun 270 degrees to face me.

"Kyaaack!"

-Kiek?

Pfsh! Startled, I hurled a lump of demonic energy, exploding it. The headless body crumbled to dust.

"Huh?"

...No idea. I fled the ruin and the village.