This world is all an illusion, and I know that.

Suddenly the world around me snapped into a textbook medieval fantasy city.

A place I'd never been. A place that doesn't exist.

"It actually worked... I was right."

Near-Infinite Illusion Theory, my theory about the afterlife, sort of.

The short version: between clinical death and full brain death, the brain can spin up an almost-infinite illusion, millions or billions of years, shaped by whatever the person believes happens after death.

If you believe in heaven, you get heaven. Believe in reincarnation, you get reborn. Believe in nothing... you get nothing. All of it vivid and real to you, even though it's just an illusion.

Consciousness ends with the brain, but there is something in between. That's the idea in a nutshell. There are a thousand arguments and paradoxes I could throw at you, but that's the baseline.

And that baseline creates a paradox: what if you die believing the theory itself? What happens then?

Well, that's what happened to me, Theo Moretti. I'm sixteen. And well, I died.

What I predicted was basically an infinite lucid dream: you know you're dead, but you can do whatever you want, and everything feels indistinguishable from life, in an extremely realistic and vivid way.

And well, I was right.

"YEAH!!! I WAS ALWAYS RIGHT!!!"

I felt a quiet hum, not in my ears, but inside my mind. Heat bloomed in my chest: not just happiness, but that bone-deep certainty when something finally clicks. Years of doubts and late-night notes snapped together into one clear truth.

"It’s true.’” I thought out loud, “I was always right.”

I don't know whether I thought it or shouted it, the words rang like they carried the weight of forever.

I'd guessed there might be something like a selection screen, a choice menu you pick from before the illusion starts. And then I was in a white void: nothing but white, endless.

Floating in front of me was a small woman.

She had pale blue hair in twin flowing ponytails and the same colour eyes. She wore a deep-blue dress shot through with silver like tiny stars, and held a wand that seemed carved from light. She was small and cute, but odd and ancient at the same time. A fairy-loli, if you must call her something.

"This is my ideal guiding entity!?" I said, a little... disappointed.

She hovered upside down and looked at me.

"Yes. Literally that. You were right, Theo, your theory was right."

"Hehe. I'm such a genius."

"Then why didn't you have friends?"

"S-shut up."

"Locked in your room for years, gaming and watching anime, until—"

"Yeah, yeah, I know."

I had basically done nothing in life but this. I couldn't believe my subconscious was listing my sins.

"Well, at least I had good grades... and I was smart, I guess. I mean, my theory was right after all."

She drifted there, a little bored, her eyes off to the side. "So, Theo, what do you want to do now?"

"It's weird to think I'm dead... not really dead, almost dead. This feels like a dream."

"Dream's a fair comparison, but it's an illusion, not a regular dream."

"Yeah, I know."

This looked and felt more vivid than any dream, hard to explain.

"Am I really going to spend millions of years in here?"

"If you wish."

She rested her cheek on her hand.

"You're frozen in time from the outside. Billions of years here will only be minutes to anyone still alive."

"Right. I know."

I'd have practically godlike freedom. An almost infinite playground. That sounded fun.

"And after all that, when the illusion ends, what then? When I truly die?"

"Don't pretend you don't know."

"It's really The Nothing?"

"Yes."

That hurt. In my theory I'd tried to stay scientific: after full brain death, there's nothing. No feeling. No thought. No time. Eternal blankness. I called it The Nothing.

"But hey, should I call you Brain?" I asked.

"You can call me whatever you want."

I built this theory because I'd been terrified of The Nothing. I'd wanted a way to avoid it while staying strictly scientific. Because honestly, I'm more scared of that place than hell. Yes, the universe has no purpose, the human being is nothing. But this is better than simply going straight to The Nothing.

Although I could do literally anything I wanted, there was only one thing I knew I had to do now that I was here.

"Okay. I want to go."

"Where?"

"You don't know? Of course I want to get isekai'd."

"Isekai'd? To where?" She sounded amused.

"You know what I mean: A medieval world, magic, powers, weird creatures. You know the type. Make it realistic! Don't give me a world rigged for me. I want to appear there and earn my place like a true isekai. And through my merit to dominate the world or something like that."

I am really excited about this. Like when a dream comes true.

"Why do you think you'll do well there, being you?"

"I..." My voice broke, and I began to stutter, looking down.

This is hard to say.

"Maybe I was just born in the wrong world. Maybe it isn't my personality, it's my surroundings..."

"You say that like you want me to agree."

"Then stop asking so many questions! You're my subconscious right!? You should know what I think!"

A small smile touched her lips.

"I do, but I like talking to you. I don't want to sound like a know-it-all."

Well she's literally that. A repository of everything I'd ever been. Tsk. Whatever.

"Alright... Brain. Teleport me."

"Sure."

She waved the wand and a doorway of white light formed a portal, a few steps from me.

"Just walk through."

"Okay."

I simply started walking towards the portal, but stopped and looked back again.

"Will I see you again?"

"You'll always see me. I generate the world you're about to enter. Everything there is produced by me. I am you. I'm always with you."

"Yeah, but... I mean, the way you are now... Brain."

"If you want, you can stay here for billions of years, maybe I'll even change shape. Don't worry about it, I'll always be your subconscious."

"Oh. Right."

I took another step.

"Wait" She interrupted my walk,"last question: Do you want me to override your memories? I can remove the knowledge that this is an illusion and make you believe you were actually isekai'd."

That might be the dumbest question I'd ever heard.

"Of course not! I might be a friendless Incel, but I have one conviction: the truth is absolute."

Maybe that sounded a bit philosophical... Kind cringe.

"The truth must be told, regardless of what it is"

"I knew you'd say that." she said

I sighed. "Ugh... see ya."

As I stepped toward the portal I heard her last words behind me.

"Learn a lot, my dear conscience."

Then I crossed.

My vision spun and spun until the white bled away.

"Wow..." Those were the only words that came out. A full medieval city opened up: wooden houses, market stalls, banners snapping, people in tunics and gowns, carts creaking, merchants shouting, and the mixed smell of wood smoke and frying food. It seems so "normal."

But, this is all being rendered in real time by my brain.

None of this is real, it's all just an illusion created by my subconscious.

It's all fake, an illusion.

It's kind of bizarre, but at the same time—

"I am so excited."