A month had passed since then. The moment I finally held the fully repaired Nichirin Blade in my hands...
As it turned out, not many of the Hashira had passed the 'Michikatsu-style' trials.
While every one of the Hashira had succeeded in manifesting the Mark in their own way, the Transparent World was a different matter entirely.
The only ones who had reached the Transparent World, aside from Rengoku, were Minase Hiyori, the Echo Hashira, and Anji, the Stone Hashira.
The only person who had reached it temporarily, much like Shimotsuki, was the Water Hashira, Sakata Gin.
Amano, who had served a relatively short tenure compared to the others, had not seen even a glimpse of the Transparent World. Even Shimotsuki had failed to enter that realm again after that singular, fleeting instance.
It seemed that, unlike Breathing styles or the Mark, the Transparent World was not something one could simply take by force or shortcut.
Still, there were now four powerful warriors capable of using the Transparent World!
Moreover, since the others had tasted a fragment of it, they would surely reach that domain one day.
Kibutsuji Muzan, you better stay right there!
Though, of course, this power came with a twenty-five-year lifespan limit.
Furthermore, the Hashira who had reached the Transparent World—myself included—had not yet attained the stage Yoriichi possessed: the ability to completely erase one's presence.
The state of perfectly controlling one's presence, battle spirit, killing intent, and emotions... I am certain this is an extension of the Transparent World.
I say this because Yoriichi told me that during our spar, the moment my Mark appeared, my presence vanished for an instant.
Even Yoriichi admitted that, in that brief moment, he could not fully read my presence.
That was when I had temporarily entered the Transparent World. This means that such a state is either synonymous with the Transparent World or its ultimate evolution.
There is no need to be impatient then. If I continue to hone my mastery of the Transparent World, I will reach it eventually.
Granted, I'll die if I don't get there within eight years, but what of it?
In any case, the only thing remaining now is the Crimson Blade.
The Crimson Blade.
A phenomenon where the blade of a Nichirin sword turns deep red and burns with intense heat.
The only person currently capable of manifesting this was, once again, Yoriichi.
Breathing styles, the Mark, the Transparent World, and now even the Crimson Blade!
Dammit! It's always Yoriichi! I have no choice but to worship him.
The 'hint' regarding the Crimson Blade was simply that when Yoriichi gripped the hilt, the blade turned red.
It sounds like utter nonsense, but looking back, hasn't it always been like this?
Sun Breathing was essentially just Yoriichi's natural way of breathing.
The Mark and the Transparent World were things he had possessed since birth.
I feel like giving myself a pat on the back for managing to obtain Breathing, the Mark, and the Transparent World using nothing but those god-awful hints.
But enough of that. The reason I want to manifest the Crimson Blade is—utility aside—because it's just plain cool.
Just by gripping it, the blade turns red and radiates heat.
A burning lightsaber... what man could possibly resist that!
And it's not like the Crimson Blade is just a limited-edition skin for the sword; it surely has some function. It's certainly better to have it than not.
I lifted my Nichirin Blade, staring at my reflection in the purple steel, and fell into thought.
What is the difference between us 'humans' and Yoriichi?
Why is it that Yoriichi can manifest the Crimson Blade?
'Throughout Heaven and Earth, I alone am the honored one.' Those words were surely meant for that man.
Are you the strongest because you are Tsugikuni Yoriichi?
Or are you Tsugikuni Yoriichi because you are the strongest?
I already knew the answer to that.
Even if Yoriichi is a being on a different level as a biological entity, it wasn't as if I couldn't use what he used.
The Mark, the Breathing, the Transparent World...
Had I not obtained all of them proudly?
And because I had obtained them, I could feel the gap between Yoriichi and myself even more acutely.
Yoriichi wasn't the strongest because of the Mark, the Breathing, or the Transparent World.
He was simply the strongest by nature, and thus the Mark, Breathing, and Transparent World were natural components of his existence.
Therefore, the Crimson Blade is surely not his exclusive domain either.
Just as Sun Breathing wasn't exclusively his.
Just as he isn't the only one to possess a Black Blade; there were those compatible with Sun Breathing even before Yoriichi, they simply hadn't discovered the Breathing technique yet.
So, there must be a specific condition to manifest the Crimson Blade, and Yoriichi simply happened to meet it by default.
What is the difference? Between him and me.
The Mark and the Transparent World aren't the conditions.
Because I possess those as well.
However, to think that Sun Breathing—the only difference left between us—is the condition... well, there are no records of previous Black Blade users ever manifesting a Crimson Blade.
Heat emanates from the blade when it turns crimson. Is it a matter of applying heat?
Yoriichi just gripped the sword.
Furthermore, Yoriichi isn't some Demon or a Pillar of Flame... how could a human generate enough temperature to heat steel just by touching it?
Even if that were true, there's no way that Yoriichi and I, both users of the Transparent World, would have failed to notice the principle behind it.
The most likely hypothesis is that it manifests when gripped while maintaining Sun Breathing.
Kuoohhh...
I activated Sun Breathing and held the sword, but the Nichirin Blade remained its original purple. No heat, nor even a hint of red, appeared.
Wait, so does it only manifest when one possesses the Transparent World, an innate Mark, and a natural aptitude for Sun Breathing while actively maintaining said breathing?
If that's the case, you might as well just call it 'Yoriichi's Exclusive Weapon Skin.'
...Let's put that hypothesis at the bottom of the list for now.
I really want to try out that Crimson Blade.
Then what could it be? The absolute difference between Yoriichi and me.
Yoriichi just held the sword, and the Crimson Blade appeared.
He held it... that phrase keeps bothering me.
Gripping the sword...
Clutching the sword...
The sword...
...?
Now that I think about it.
Something suddenly comes to mind from that spar with Yoriichi.
Was it from the moment Yoriichi gripped the wooden sword? Throughout the duel, I heard an irritating sound.
At the time, I was too focused on Yoriichi to pay it much mind, but it was a *crack-crunch* sound of something being crushed near Yoriichi's hand.
I heard it right until the moment our blades clashed, didn't I?
Yoriichi's hand wouldn't be the thing crumbling, so that means the sound was coming from Yoriichi's wooden sword.
Why did his wooden sword make such a sound?
And while it only passed through my mind for a second, my wooden sword had been cleanly sliced through at the point of impact, whereas Yoriichi's wooden sword had snapped at the hilt.
Could the answer be there? A decisive hint!
Yoriichi's claim that it manifested just because he gripped it.
That means Yoriichi likely picked up the Nichirin Blade without any particular thought.
And yet, just by holding a wooden sword, it made a crushing sound?
I remembered. Another difference between Yoriichi and other humans.
Yoriichi was a monster who could knock out trained samurai in four strikes at the age of seven.
Even if he was physically enhanced by Sun Breathing, he was just insanely strong regardless.
If—just purely 'if'—
What if the condition for the Crimson Blade's manifestation is immense grip strength?
It sounds like a rather deflating condition.
However, if it's true, it explains why the Crimson Blade is a hidden function that only activates when a Nichirin Blade meets specific conditions.
It also explains why many have wielded Nichirin Blades without breathing techniques, yet none have ever manifested the Crimson Blade.
A katana is a sword meant to be held and swung lightly.
What madman would grip it with all his might as if it were a longsword?
Moreover, even if someone did grip it that hard, I doubt their strength would surpass Yoriichi's grip.
An average adult's grip strength is roughly 50kg. The grip strength of an orangutan, which can tear a man apart, is 193kg.
Yoriichi could probably tear that orangutan apart with ease.
And it's only recently that the Hashira of the Demon Slayer Corps have come to possess both Breathing styles and Marks that enhance their physical abilities simultaneously.
It bothers me that Minase, who can transform into a Demon, hasn't manifested the Crimson Blade, but she's a Thunder Breathing user who concentrates all her power into her legs, and she fights by coating her sword in frost-based Blood Demon Arts...
But could it really be just grip strength?
Well, if it's not, it's not.
With half-conviction and half-doubt, I concentrated every ounce of my strength into the hand holding the Nichirin Blade, applying a crushing grip.
As expected, the Nichirin Blade remained unchanged.
Hah, see? It doesn't wor—
Sssssssssss...
...
Suddenly, the blade of the Nichirin sword began to dye itself red, and a searing heat started to radiate from it.
Holy hell, it actually works.
By the way...
Yoriichi made a Crimson Blade even faster than I did, just by holding it casually without a second thought?
In that spar, Yoriichi's wooden sword didn't break because of Moon Breathing, Eighth Form: 'Tensa Zangetsu · Getsuga Tensho'; the wooden sword just couldn't withstand Yoriichi's grip strength?
I mean, more importantly... Sister-in-law, how on earth did you share a bed with someone possessing such physical specs?
The one we should be worshipping isn't Yoriichi, it's Uta!