I Defeated the Demon King on Day One and Retired
1

Chapter 1

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Part 1. Let’s Talk About My Childhood.

  • I was born with talent.

  • An overwhelming talent that surpassed anyone else in the world when it came to handling the tool called the human body.

“…Oh no. This is bad.”

“Mom, what’s wrong?”

“Ah, it’s just… I think I lost the key. Your dad’s almost home anyway, so why don’t we go somewhere and grab something tasty while we wait?”

“…Mom. Can I break this?”

“Hm? Break? Break what?”

“The lock.”

  • And that was the first time I realized I had talent.

“You’re going to break a lock? You? How?”

“Like this.”

Crunch! Clang!

  • I was five years old when I twisted and shattered the padlock, barehanded, right in front of my mom. It had been put there to replace the broken door lock.

Her eyes went wide as she asked, “How did you do that?”

“Hm? It just works like this. You can’t do it, Mom?”

That night, after tucking my younger sibling into bed, my parents came back to test me. They watched, mouths agape, as one bizarre spectacle after another unfolded in my hands.

Snapping bricks with a flick of a finger. Punching a hole through a frying pan with a toothpick. Breaking a chair leg clean through a wall.

“A-amazing… how is this…?”

When my dad saw me slice chunks off a granite block—something we’d been using as a plant stand in the yard—with nothing more than a stationery cutter, he finally grabbed my arms tightly, his voice quivering with panic.

“M-magic? Superpowers? How on earth can you do this?”

I thought for a while about how to answer. In the end, all I could say was:

“You just have to do it right.”

“D-do it… right?”

“Yeah. Right.”


Part 2. Let’s Talk About My Elementary School Days.

As time passed, my parents realized that my gift wasn’t limited to one specific area. It covered every possible way the body could move. And it wasn’t something that could be measured by words like “genius.” It was something far more terrifying.

So whenever they had the chance, they would remind me:

  • You can probably do anything, and become anything.

  • Soccer, baseball, tennis… as long as you know the rules, you could become a player unlike any in history.

  • That’s why what you need to do isn’t sharpening your talent or making it grow.

  • You have to make sure that your talent never crosses the “line” society has drawn, that it never spills over the wall of common sense.

  • If you don’t… people will fear you. You’ll end up alone.

  • Promise us. Until you’re sure you won’t be controlled by your talent… until you’re grown enough to understand the world and make proper judgments… never show your power to others.

It was too complicated for me to fully understand, but I was naturally mild and obedient, so I listened to them.

Still, as I grew older and started to grasp their worries, one question lingered in my mind:

  • Alone? Isn’t that… fine?

Part 3. Let’s Talk About My Middle School Days.

Even subconsciously, I kept looking for ways to avoid crossing that “line” my parents had spoken of.

In the end, I found one.

I created a clear mental image of “myself inside the line” and “myself outside the line.” And then I built a switch in my mind that let me flip between them.

As a trigger for the switch, I chose something simple but unusual for me: holding a knife in a reverse grip.

Switch off: the realm of the ordinary.

Switch on: the realm beyond human.

It took some trial and error, but in the end, my method worked flawlessly.

I held the knife in a reverse grip.

Click.

A dull grinding sound echoed in my head, and I—only I—became the center of the world.

Everything in existence realigned and reassembled around me.

The feeling was godlike—an overwhelming sense of omnipotence.

I didn’t even need to test it to know. Right then, with just a kitchen knife, I could probably deflect bullets without a scratch.

It wasn’t difficult. It didn’t require training. It was simply… natural.

Plink.

A droplet fell from the sink faucet. The knife in my hand flashed.

Shhk!

The drop split into eight fragments in that single instant, only to come together again as if nothing had happened, continuing its fall.

I tracked its path with my eyes, in the endlessly slowed time, and a thought came to me.

“Why can’t people do something this simple? This obvious?”

And then…

“Do I really have to accept that I’m the same as those ordinary people who can’t even do this?”

Clatter.

Leaving that unanswerable question behind, I quietly set the knife down on the table.


Part 4. Let’s Talk About My High School Days.

I didn’t want to sound like some brooding edgelord, but…

  • By then, I had become terrifyingly strong.

I didn’t need effort.

I didn’t throw punches ten thousand times a day.

I didn’t sit in meditation like some hermit master, chasing the way of the sword.

Just breathing was enough to make me stronger.

That alone was enough to leap past the tens of thousands of hours of blood, sweat, and study that ordinary people had to endure.

It was the monster inside me, wearing the name “talent.”

Thud!

“Hey. Move over, I want to sit there.”

A thug from the next class, notorious for being trouble, smacked me on the back of the head while I was quietly solving math problems, demanding my seat.

I decided to move without a fuss.

Snapping a punk’s arms or legs would’ve been nothing to me, but I hated noisy drama.

“You bastard, look at you. I come here all the time, and you still don’t get up the second you see me? You spineless piece of shit.”

…Yeah. That was, until he decided to run his filthy mouth.

“Phew…”

I slowly stood up, staring blankly at his face for a moment…

Click.

…then quietly pulled out the knife blade of the multitool from my pocket.

The air shifted, filled with an overwhelming exhilaration.

Killing intent.

“Ghk…”

“Khuk…”

“Grrk…”

Just by letting a surge of fury leak out, students in the classroom and the hallway rolled their eyes back, fainting without knowing why.

Bang!!

The punk, half-choking from being directly exposed to that aura, had his head slammed into the desk once. I held him there, debating how to deal with this clueless piece of trash.

Then, a sudden urge boiled up.

‘…Should I just kill him?’

And the inner demon called talent whispered inside my head.^[TL/N: In Buddhist/Daoist thought, this refers to the dark impulses or obsessions born from one’s own heart. Here, the protagonist identifies his overwhelming talent itself as his inner demon — a monster wearing the name of ‘talent.’)

‘Yes. Kill him.’

‘Crime? Don’t be ridiculous. Don’t apply lofty standards like good and evil to lowly vermin like that. Those only matter to beings equal to you.’

‘You don’t really think that half-formed insect is the same kind of creature as you, do you?’

Grip…

Disgust. Contempt. Bloodlust. My hand clenched tighter around his throat.

But then—

“Ghhhk… please… don’t….”

That final rasp, teetering between life and death, dragged my mind back into place.

“…Ah, damn.”

Startled, I released his neck. Then, realizing what I had nearly done, I let out a hollow laugh.

“Shit. I must be completely out of my mind.”

Yeah. I had almost killed him. Without the slightest bit of guilt. Because I hadn’t seen him as human, there had been no hesitation in my hand.

And that’s when it hit me.

The monster called talent had already half-devoured me. It wasn’t me wielding talent anymore. Talent had put on my skin and started living as me.

If I left it unchecked, that whisper egging me on would soon become my true desire.

Clang!!

I drove the multitool blade into the desk, snapping it in half, and let out a long sigh.

“Phew. Let’s end the edge-lord phase right here.”

Yeah. Even without flipping the switch, I could already display abilities at the limit of humanity. That was enough. Enough to live a decent life, without standing out, enjoying the world as it was.

It’d be… frustrating. No, suffocating, really. But that was fine. Everyone said the same thing, right? Nobody gets to live only doing what they want.

Click.

From that day on, I never flipped the “switch” again.


Part 5. Let’s Talk About My College Days.

At twenty-two years old.

I sat slumped on a hospital bench, a canned coffee clutched in my hand, staring blankly up at the sky.

“Terminal colon cancer.”

“As you can see here… the spread has already reached the liver through the portal vein.”

The doctor’s clinical explanation came with a death sentence.

“Ha… haha. Life, huh. Did I sell out my country in a past life or something?”

What made it worse was that it wasn’t just me. Mom and my younger sister had both already been fighting cancer since last year.

‘Three out of five family members with terminal cancer? How the hell can misfortune pile up like this? What a goddamn joke…!’

At least unlike Mom, my younger sister still had a chance at treatment… though the outlook wasn’t exactly bright.

I shut my eyes tight, remembering how Mom had broken down, sobbing that it was her fault—that the cancer had been passed down through family genetics—when my sister was diagnosed.

‘I can’t tell Mom for now. If I do, she might really make a terrible choice.’

‘I should keep it from Dad and my brother too. They’re barely holding on as it is. If I tell them I’m terminal as well, their sanity will crumble like a cookie.’

I fidgeted with the multitool in my hand, its blade still broken.

“Haa… What do I do?”

And then, a bitter laugh slipped out.

Now that it had come to this, the talent I had been so wary of suddenly felt like nothing special.

What use was splitting mountains or parting seas with a single stroke, if I couldn’t even beat something as stupid as cancer?

I sneered at the talent curled up inside me.

“You’ve got shitty luck too, don’t you? Stuck with a dying guy like me, never getting your chance to shine. Would’ve been better if you’d crawled into some chosen hero in a fantasy world instead. Right?”

And that was when it happened.

[Are you interested in a world beyond this one?]

“…!!!”

With a strange woman’s voice, the entire world froze into a dull shade of gray.

I was no exception. Only my eyeballs twitched, the rest of me feeling like it was trapped in sticky glue.

Then—

[Don’t be too alarmed.]

…a being I had never seen before revealed herself before me.

She wore a pitch-black women’s suit that resembled mourning clothes, long silver hair flowing down her back, her eyes shimmering the same silver. Beautiful, but wrong.

Her outfit was plain enough, but there was no mistaking it—she wasn’t human.

And the proof? She was floating about thirty centimeters off the ground.


Part 6. Let’s Talk About My Meeting with a Strange Woman.

The woman smiled at me.

[I only accelerated your thoughts a little. It feels like your body can’t move because it can’t keep up with how fast your mind is working.]

‘What is this? A delusion? A hallucination? Since when did I start showing schizophrenic symptoms?’

[No. I’m neither your delusion nor your hallucination. I really exist here.]

‘She can even read my thoughts?’

[I can only skim surface thoughts. It’s not like I’d know what’s inside that suspicious “New Folder” of videos on your laptop desktop, for example.]

…I had a mountain of retorts, but I swallowed them down and asked the one question that mattered.

‘What are you?’

[Hmm, let’s see. If I had to define it, I’m a transcendent being here to take you to a new world.]

A new world? Take me? A transcendent being?

‘…Ah. I get it now. With that outfit and those strange powers… you’re a Grim Reaper, aren’t you? Or maybe I should call you a Shinigami, since you’ve got more of a Western vibe?’

[Hm? Grim Reaper? Shinigami? No, I think you’re misunderstanding—]

At that moment, my twitching finger finally succeeded in pulling out the ‘fork’ from the multitool.

Clack!

It wasn’t a knife. It wasn’t the trigger.

But it didn’t matter. The trigger had only ever been a convenience. If I wanted, I could flip the switch without it.

That was my true self—unbound by rules.

Click.

With a heavy metallic groan, the world flipped, reorganizing itself around me.

Overwhelming omnipotence filled every fiber of my being. A sense of release.

‘Ahh…’

It had been three years since I last flipped the switch, but my senses and technique weren’t dulled. They were sharper than ever.

I grinned, flashing white teeth at the woman who still hadn’t caught up with the situation.

“Alright then. Let’s have a fight, Miss Grim Reaper.”

[…Eh?!]

#1 Chapter 1

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