Demon Slayer is the property of Koyoharu Gotouge. I do not own any of these characters - I'm just a fan who likes to write.

The principle of a universe one-thousand years in the making:

To receive something that you think is of value you must give something that the world deems as equal in value. The subjective in comparison to the objective.

And there is nothing worth more than a life, and there is nothing worth more than the memory of a life.

February 1922
Fuji Musume

There was a time when I'd lost everything, and I didn't know what, only knew something was gone. It was not I who made the choice to relinquish it, but if I was given it again now, I wouldn't try to change the course of history, either. Because I did not know the magnitude of what was taken from me, innately I did not have a drive to regain it. Then I did, then I realised, then I fought to get it back. But to receive something that you think is of value you must give something that the world deems as equal in value; the subjective in comparison to the objective. That was my undoing, but it was another who took the brunt of my punishment in attempting to make an unequal trade. A punishment, that today, will come into fruition.

"Did you know, Giyuu? On the other side of this sea is the demon enemy. But not our enemy."

It was not a sea, but a lake. On the other side of this lake was the estate of Ubuyashiki Kagaya, an eternal, iconically criss-crossed complex, now evaporated by fire and a-burst in a body of it that whipped with the wind. On this side of the lake was a patch of nature, among which stood the man with the forever blue eyes, the tied-up hair, the mismatched haori that too many would come to associate with me too dearly.

Here was one such.

Giyuu – how long has it been since she called me that? For the longest time it was 'Tomioka-san', but that was too formal, too stringent, too befitting of the gap that grew between us. I looked behind me and saw Kochou Shinobu leaning on her sword, staring; the eyes without pupils, the iridescent butterfly clip that now shone only white in the moonlight.

胡蝶 しのぶ
Kochou Shinobu
"butterfly, recall"

"I ain't ever had good memories around lakes," I said. "They always seem to be bad luck when I meet somebody by one."

I looked on at the fire, only looked, because though the man and his family who burned with it was the central figure in the entirety of the corps I'd spent my entire life in, entire life running away from, I felt no incentive to save them. The boy I was three years ago would've tried, maybe, tried to defy his future one more time, but the truth is that Ubuyashiki Kagaya was already dead, and I knew his death was coming and I did nothing to stop it because I could do nothing.

産屋敷 耀哉
Ubuyashiki Kagaya
"maternity, gleam"

and

冨岡 義勇
Tomioka Giyuu
"wealth, courage"

"How many times does this make, now?" I said. "One-thousand… or ten? Guess it doesn't matter."

"What?" Shinobu replied.

I waved her off, and put my hands in my pockets and stood over Shinobu. I scrutinised her a while, and even I'm not entirely sure why, but something in her expression struck a note in me and I realised.

"You knew Kagaya was gonna go out like this? That's why you're so calm, isn't it?"

"I knew 'cause you knew."

Of course, for we had known each other too long not to. Ten years of hell and heaven on earth had linked us intrinsically, though I will add I knew Shinobu better than she knew me.

"You look tired," Shinobu started. "How'd you sleep?"

"I don't know. I had dreams," I replied.

"What kinda dreams?"

"Long dreams of older days. When it was just us. Dreams that didn't make any sense… some that scared me."

"Nightmares?"

"Maybe."

"What's up? You ain't very talkative today."

"I never am, Shinobu."

"But now more so."

"No reason for it."

I put a hand between us to silence her, maybe because I could sense my own irritation, maybe so that she wouldn't have to lest it bubbled over. But I immediately felt bad, and swiftly retracted it.

"Know why I came here?" she asked.

I noticed she held her one arm stiff, fingers cuffed over her sleeve. Indeed I did know, and even though I'd stated before that we were linked intuitively in mind and that I was able to read her as a result, the same could not be said for the reverse. I already knew what was hidden behind that wrist, and that she could not have anticipated that. Yet still I feigned ignorance, and then she produced the letter from her sleeve, fashioned out of parchment of purity, stamped with purple wax upon which embossed was the crest of wisteria.

"For you." She gave it to me, but kept her hands on it a while. "But don't read it now. Only after all this." Then she let go.

It was a hefty envelope, chock-full with an amount of paper that far exceeded its intended capacity. It brought to mind the image of a brick, and befitting of one, the wad remained stiff as I waved it around.

"What's this for?" I asked. Shinobu did not answer, and I saw her purple eyes fall on the ground, at her shifting feet. After much waiting, I beckoned her again.

"That exchange I made three or four years ago… the time has come for me to pay up. But before I did, I wanted to leave something behind. There ain't much in that letter… just a bunch of reminiscing. But it felt good writing it, you know? I can't explain it."

How could I forget that? Many a time have I tried to force myself to, or at the very least hide it under the thin veil of time and keep it there for as long as my own conscience would let me. In the gap years between now and the conclusion of my old self I have learned to let the world pass me by, hoping, that at some point, it would take the bad memories along with it. Memories of my own arrogance, and the chastisement it brought upon Shinobu three years ago as punishment for it. To God and his world they deem it a fair trade, and even I cannot call it unfair. Perhaps that is what I hate myself for it so. There's nothing, no-one to hold at fault except the enemy on the other side of this lake, and I. Those who think the world is theirs, but don't have anything to give for it. Even so, as for her…

"Because four years ago, Giyuu, you saw the truth. That my fate had been set from the start, and that I was going to die."

That's right.

When I rediscovered everything I'd lost, there was a price to keep it upon leaving that place; a price I couldn't pay. But Shinobu was there, and Shinobu could. She filled in for me, and pensively, she held up two of the foremost aspects that defined a universe one-thousand years in the making:

The one thing that was most important to the world, and the one thing that was most important to her.

Trivia:

藤娘
Fuji Musume
"Wisteria Maiden"

A famous Kabuki performance dating back to 1826, depicting a fabulous young girl who falls in love for the first time. Each section of the play depicts different stages of the girl's affection: first an energetic opening dance mimicking the joy of fresh love, then a somber mime display as jealousy seeps in, then a crashing portrait of heartbreak stemming from betrayal.

The Fuji Musume is named such because the girl is meant to embody the spirit of the Wisteria flower: rapturous, blissful, forever subject to the seasons, or her emotions. The Fuji Musume herself starts as a painting of a woman dangling a Wisteria branch on her shoulder, displayed on the streets of feudal Kyoto. Upon catching the eye of a male passerby, she finds it in herself to leave the painting and come to life. Falling deeper and deeper into infatuation with the man, she writes him multiple letters, all going unanswered. Eventually, despair takes over the maiden and heartbroken, she returns to the world inside the painting.

Accompanying the performance all throughout are a range of suggestive images that reference the sensual nature of the pine tree that supports the wisteria branch, their stems entwined, akin to two lovers sleeping together. To this day the play remains a hallmark of Kabuki theater, with there being many renditions of it, and in a way, the true meaning of the piece is still under debate.

Have you heard of the Fuji Musume? It was Shinobu who introduced me to it. She was always one to be fond of books, movies, plays, theatre, the like. I remember, once, I accompanied her to the outskirts of the city in which we both lived, to see a Kabuki performance that was purportedly, the only one in its league of magnificence. We were taken to a huge, dazzling hall and given our seats. I watched as the actors filed onto the stage – both men and women, contrary to the male-only nature of the art – and the last lady who came in and who balanced on her shoulder the radiant branch of Wisteria, my eyes were on her. She went to the centre of the platform, splayed her arms, and announced the name of the performance in a high, shrieking voice: Fuji Musume. Then the lights went dim, the drums began to beat, and she was initiated. Transported to the streets of old Kyoto, I watched, as she began to dance…

Say, Shinobu's become a bit like that Fuji Musume now, hasn't she?

She's going back to the world inside the painting, and I –

I'm going to do nothing to stop it.

"I've imbued myself with Wisteria, Giyuu. A whole thirty-seven kilograms* of it, exactly equivalent to my worth in body weight. No demon will survive if they absorb me. Not even the emperor, if he was still here. The world expects me to lie down and embrace death… but I'll bring him with me. It's only fair, right? If they want to take my life, then I'll take his!"

*eighty-two pounds

"It's also why I haven't been coming to Hashira training," Shinobu continued. "Like this, it's tiring to do anything, y'know? My body's all heavy…" – even now, she's sweating all around, and sucking in air – "but in all that free time I wrote this letter, so I can't say it was wasted. Hey, Giyuu…"

I'd phased out into a dream by which now I've already forgotten, and I'm back in the present. How long was I out? Shinobu's standing before me, leaning forward, face half-lit. For a moment we're still, then I realised the weight of the situation I was in, that Shinobu had proclaimed her own death, and that here I stood, doing nothing, like I always have.

In any other world, if I were able to fight –

I would not have it.

But I knew, more than anyone, that it was inevitable.

That day in limbo, both Shinobu Kochou and Giyuu Tomioka were given a choice:

The life that I were to lose in the winter of the final year of the Great War -

Or the memory of a life Shinobu had grown to hold as the single dearest thing in her, as well as her own.

Shinobu Kochou chose the latter, and that is why we stand here today. And since her will was executed as the will of God I can do nothing to avert it. That is why I cannot fight. That is why I do not fight. To try to contest God means to play with the path he has set out for you – a path that can so easily go sideways, so easily end suddenly.

Yet there is one thing I can do.

From when we were young she was always the blissful one. Maybe, just maybe, like a sibling to me; a little sister. That is why even now I wonder if I truly love her. It's cruel of me, isn't it? It was only yesterday – no, the day-before-yesterday – that I gave in to her. I fulfilled her long unrequited love for me before it would all come to a screeching halt. I wasn't in a position to deny her, but that isn't why I did it.

I like to think that it was simply and only to make her happy.

Even though it wasn't, and when I eloped with her, kissed her, under that pale, perfect moon she would never see again, I felt something, something akin to the childish game of love, and I hated myself for it.

"You'll read the letter only when I'm gone, Giyuu."

"You told me already."

"And there won't be tears."

"Already paid them."

"Then I'll be going."

"For how long?"

"A few hours. Or eight years. Nobody knows. But we'll meet again, and that'll be the end of it. So, goodnight, Giyuu."

She slides out of my arms and starts to pad away, still facing me, until she turns round and begins picking up speed and I keep on watching to see if she ever looks back, but she doesn't. She disappears under the pillow of winter fog and fire and I'm left wondering to myself why, when she started crying, did she then break away from me, why I wasn't fighting to divert her fate one last time, why I was shedding tears for someone I knew was going to die and had so for the better part of my miserable life, why – I let go of her at all.