"You're certainly generous... forging dozens of Sun Blades in one go. I'm sure our lord will be delighted when he hears the news."
On the way back, Cho was in high spirits.
Because she too had received a Sun Blade — a gift from Kobe Hikaru, tacitly permitted by the smiths of the Swordsmith Village, as repayment for guiding him — even though guiding him had simply been her duty to begin with.
Though she was only a support-division Kakushi, Cho had always longed to carry a Sun Blade of her own, longed to stand on the front line as a Demon-slaying swordsman. She'd simply never had the ability for it.
Besides that—
if Kobe Hikaru hadn't firmly refused, the smiths of the Swordsmith Village would have all but gotten down on their knees, begging him to stay and teach them the art of forging.
But Kobe Hikaru knew his own limits well enough. Strip away the system, and in terms of pure forging skill alone, he likely wasn't all that far ahead of smiths who had spent their entire lives at the anvil.
So naturally, he'd turned them down.
He left the blades he'd forged with the Demon Slayer Corps,
keeping only the single most crucial, most essential one for himself,
and, as a reject, one more besides.
Afterward, Kobe Hikaru made his way back to the Demon Slayer Corps — having just gotten his hands on a Sun Blade, he needed some time to familiarize himself with it.
And then, to work on the bond.
The rear courtyard of the Ubuyashiki Mansion, headquarters of the Demon Slayer Corps.
Wisteria blossoms hung from the trellis overhead, forming a natural curtain of flowers, their pale purple clusters swaying faintly in the morning light.
Kobe Hikaru sat cross-legged on a stone platform in the courtyard.
A blade lay across his knees.
A Sun Blade.
Its sheath was deep crimson, the hilt wrapped in white silk cord, with a thumb-sized piece of Scarlet Crimson Ore set into the pommel.
The blade's color was unusual — neither the silver-white of ordinary steel nor the lacquer-black of dark iron, but tinted with a faint orange sheen.
That color came from the sunlight the Scarlet Crimson Iron Sand and Scarlet Crimson Ore had absorbed through year-round exposure, seeped into the very structure of the metal.
The Sun Blade was also known as the color-shifting blade.
The signature weapon of the Demon Slayer Corps — yet this one had been forged by Kobe Hikaru's own hand.
Its raw material was Scarlet Crimson Iron Sand and Scarlet Crimson Ore gathered from the Sunlit Mountain, ore that had drunk in the sun's energy through years of exposure, then forged into the blade through a specialized technique.
Its cuts carried the property of sunlight — the only weapon known to date that could sever a vengeful Demon's undying regeneration completely, even in the hands of an ordinary swordsman.
And its color would shift according to the nature of whoever wielded it.
And so, at this moment—
the status panel popped up.
[Sun Blade (Unbonded)]
[Quality: Half-Yokai Weapon]
[Description: A Demon-slaying blade forged from Scarlet Crimson Iron Sand and Scarlet Crimson Ore, its body holding sunlight energy accumulated over the years. Its material lifts it above an ordinary weapon in quality, yet it lacks a blade soul and does not qualify as a yokai weapon.]
[Current Favourability: 15 (Familiar)]
Because it had been forged from ore and iron he himself had won over, it carried a measure of favourability from birth.
It was, remarkably, a half-yokai weapon.
Which made perfect sense.
The Sun Blade's raw materials were extraordinary.
The Scarlet Crimson Ore had absorbed centuries of sunlight, nurturing within it a rich spiritual nature.
Add to that Kobe Hikaru's unique forging method, which had preserved nearly all of that energy intact, and in essence, the blade had very nearly become a yokai in its own right.
It fell just short — but it truly possessed properties no ordinary weapon could claim.
So it was, by nature, a half-yokai weapon.
More than that — a yokai weapon that could undergo metamorphosis at any moment.
None of the other Sun Blades had this quality. Not even the ones he'd given away.
Kobe Hikaru laid his palm over the sheath and let his yokai power seep in.
Hmm—
the blade trembled once, the faintest shudder, like someone stirring at a touch in their sleep.
And then nothing more.
It was only a half-yokai weapon, after all — its response to yokai aura was nowhere near as sensitive as a true yokai weapon's.
It had been born to slay Demons. The sunlight energy within it didn't repel yokai aura outright, but the two ran in nearly opposite directions.
Even with a baseline of favourability already in place, winning this blade over wouldn't be simple.
But it wouldn't be difficult either.
Because Kobe Hikaru had the Blood-Fire Mutation.
Fire belonged to yang.
Even though the yokai fire running through him traced back to Totosai, and was, at its root, a product of foul aura, the nature of fire itself was universal — heat, light, burning.
These qualities held the possibility of resonance with the sunlight energy inside the Sun Blade.
What he needed to do was find that point of resonance.
Sure enough,
the panel flickered.
[Sun Blade: Favourability +1]
[Current Favourability: 16 (Aware)]
It had begun.
He was getting better and better at this.
Kobe Hikaru felt himself sinking ever deeper down the road of being a yokai playboy.
At the same time, on the other side of the rear courtyard—
Tsugikuni Yoriichi sat on the wooden floor of the corridor, bare feet resting on the edge of the steps, a blade likewise laid across his knees.
Not the woodcutting hatchet he normally used.
But a Sun Blade.
Technically, Tsugikuni Yoriichi hadn't yet formally joined the ranks of the Demon Slayer Corps, and by the rules, shouldn't have had a Sun Blade at all.
But then again, rules had a way of bending around him.
The blade, naturally, had been a gift from Kobe Hikaru.
It was the reject Kobe Hikaru had forged — 'reject' in name only, since it still far surpassed an ordinary Sun Blade. It remained a mundane weapon, nothing more, but it was more than capable of perfectly carrying Tsugikuni Yoriichi's intent.
Ubuyashiki, for his part, had let it pass without comment.
The head of the Demon Slayer Corps seemed gentle on the surface, but he was, in truth, remarkably decisive — decisive to the point of being almost cold-blooded.
This blade.
The situation as it stood.
And then there was the matter of Tsugikuni Yoriichi's wife, Uta, already settled in a quiet room within the mansion's inner courtyard, tended by the Ubuyashiki household's maids.
A midwife had been arranged, ready at a moment's notice — Corps headquarters kept physicians on hand, and since other Corps members' families lived there too, it was equipped with an experienced midwife as well.
Uta was safe.
So was the child.
For this, Tsugikuni Yoriichi was grateful to Kobe Hikaru — and, by extension, to the Demon Slayer Corps as well.
Once he'd learned that these people existed for the sole purpose of destroying the vengeful Demons that preyed on others, he'd felt he ought to lend them his strength.
The red-haired young man lifted his head, his deep crimson eyes following the wisteria petals drifting through the courtyard.
Then he closed his eyes.
Within his Transparent World, every current of air through the mansion lay clear before him — the path of each breeze, the rhythm of every breath drawn by everyone present, the growth of every wisteria vine.
But the Transparent World never held only the present.
It held the past as well.
His thoughts drifted back to that night.
He was thinking.
Thinking about the vengeful Demons.
Thinking about the old man he'd subdued, then let go — a chang, a human under a vengeful Demon's control.
The mere existence of such a thing meant vengeful Demons had intelligence, organization, purpose.
He thought too of the Demon Kobe Hikaru had shattered with a single strike — by the time he'd reached the scene, all that remained was a scorched black gash in the earth and a lingering stench of rot in the air.
The thing had died too cleanly — cleanly enough to remind him of the shattered anatomical scrolls he'd seen as a boy in the Tsugikuni family's swordsmanship hall.
Those things feared the sun.
That much the Demon Slayer Corps swordsmen had told him.
They said vengeful Demons could only move at night — that once caught in sunlight, they'd burn to ash and nothing.
That was why the Demon Slayer Corps wielded blades charged with the sun's own energy.
Yoriichi lowered his gaze to the blade in his hands.
A Sun Blade.
A blade forged from some kind of sunlight-absorbing ore — genuinely effective against those vengeful Demons.
But that clearly wasn't enough.
A blade with the sun's power alone still wasn't a sure thing.
By Master Kobe Hikaru's account, and Master Rengoku's as well, casualty rates among Demon Slayer Corps swordsmen remained high.
What if — he used the breathing technique he knew best to imitate the sun, and became the sun himself?
Wield such a blade in time with a sun-like breathing rhythm, burning the oxygen in his lungs to its very limit in the instant of the swing, wringing his body's potential dry — would a cut delivered like that truly carry the sun's own heat?
The idea took shape in his mind, growing clearer by the moment.
He closed his eyes.
And adjusted his breathing.
Different from the raw, unrefined breathing he'd used before.
This was deeper, slower, more sustained — pulling air down into the very depths of his lungs on the inhale, driving every last trace of spent breath out on the exhale.
The rhythm was steady and unbroken, like waves breaking on a shore, like wind moving through a valley.
It was a technique he'd mastered naturally since childhood.
He had no idea it could be called a Breathing Style, no idea he was the only person in the world who could breathe this way.
He knew only that, breathing like this, his body grew lighter, his sight sharpened, his hands steadied, and his strength swelled beyond its usual measure.
Something clicked into place within him, and he rose abruptly to his feet.
He lifted the blade in his hand.
The iron edge caught none of the morning light, dull and unremarkable.
But the breathing of the one who held it had changed.
Deep, dense, the same as before, and yet carrying an entirely different rhythm.
On the inhale, his chest seemed to hold the whole sky within it.
On the exhale, heat seeped out through his pores, gathering across his skin in a haze almost visible to the naked eye.
He raised the blade, slow.
Then brought it down.
Just one stroke.
Slow. Light.
But the air the blade cut through — scorched.
Genuinely scorched.
Along the path the edge traced, the air heated instantly to a searing temperature, forming a fleeting streak of orange-red afterimage.
Like a trailing echo of sunlight.
It was no trick of the eye, no illusion.
Because Tsugikuni Yoriichi's single cut had faintly drawn together the energies of heaven and earth… in this blended world, the so-called Breathing Style truly carried power of its own.
From the far end of the corridor came a sharp intake of breath.
Rengoku Jinjuro stood there — no one had noticed him arrive — his crow mask pulled off, his eyes wide beneath heavy brows.
"Master Tsugikuni — what... was that?"
Though the man before him was, on paper, nothing more than a woodcutter, Rengoku Jinjuro had witnessed his strength firsthand, and held him in genuine respect.
Yoriichi turned his head to look at him.
He thought for a moment, as if searching for the right words.
In the end, he settled on a name:
"Breathing Style."
Simple. Direct.
"It uses breath as its foundation, to amplify everything the body can do."
"And what I just used... maybe you could call it the Breath of the Sun. A breathing style that mimics the sun's own changes."
Rengoku Jinjuro's jaw worked soundlessly.
He wasn't yet a Hashira, but he was already, in practice, one of the strongest members the current Demon Slayer Corps had.
But even he had never seen anything like this — breath alone, amplifying one's own strength.
The samurai he knew, the sword schools he knew, at most used breath to manage their air, to keep pace in a fight. Nothing more!
His hand, so used to gripping a Sun Blade, was trembling faintly.
Because he sensed this might well be the way — a method that could let humans stand directly against vengeful Demons, and, if it came to it, even match yokai.
Not through numbers, not through traps, not through throwing away lives by the dozen.
But through strength of one's own alone!
"Could... you teach me?"
The words spilled out of him before he could stop them.
Yoriichi looked at him.
"I can."
No hesitation. No holding back.
The thought became action at once.
He felt it was only right — his way of repaying the Demon Slayer Corps for their help.
He turned the Sun Blade around, offering the hilt to Rengoku Jinjuro. "Start with the breath. Draw in a deep breath, and let the air fill every corner of your chest."
"Then let it out, slowly."
"As you exhale, feel the blood inside you — let it move, quicken, grow hot."
"Remember that feeling."
"That's the starting point."
Rengoku Jinjuro took the blade and drew a deep breath.
He tried.
Then broke into violent coughing.
He'd failed, unsurprisingly.
But Rengoku Jinjuro's eyes only burned brighter — startlingly bright, bright enough that it was almost hard to meet them.
He'd felt it. He'd truly felt it.
All the while, on the stone platform across the courtyard—
Kobe Hikaru, even as he poured yokai power into winning over the Sun Blade, was watching the scene from the corner of his eye.
His crimson demon eyes narrowed slightly.
He was watching.
And he was learning.
That Tsugikuni Yoriichi had just created the Breath of the Sun on the spot didn't surprise Kobe Hikaru in the least.
Even setting aside the original Demon Slayer: Kimetsu no Yaiba, judging purely from what he'd witnessed so far, Kobe Hikaru had already come to understand something of who Tsugikuni Yoriichi was.
The man was strong.
Strong by nature — and strong through what he'd made of himself.
Tsugikuni Yoriichi's intent... was nothingness.
No desire. No craving. No self.
And, in that, limitless room to grow.
The ceiling of his strength depended on his surroundings — depended, above all, on the people who pushed him forward.
That was why, though he'd lived in this blended world all along, Tsugikuni Yoriichi hadn't grown especially powerful — his environment simply hadn't demanded it of him.
But now his environment had changed.
What was owed to him would come, in time.
As for the Breathing Style, Kobe Hikaru found himself just as interested in it as he had been in the Sun Blade. As he'd noted before, breathing techniques turned up in every world, every discipline — he'd already seen no shortage of them himself. Even his beloved, Kikyo, whom many called the greatest shrine maiden of the Sengoku era, could channel power through breath as well.
Though what Kikyo breathed was a purer form of qi, one order higher — with it, she could draw on spiritual power and project it beyond the body itself.
The Breathing Style, by contrast, worked the qi caught between the pure and the foul — the vital breath of living creatures.
The difference in purity was stark, plain to see at a glance, and the two hardly meshed at all.
But that didn't mean Tsugikuni Yoriichi's Breathing Style was without value.
It fell short of the very peak, but stood high above the rest — the Breathing Style might not measure up to Kikyo, but between those two extremes lay the mass of humanity, and within that mass, it made a mortal exceptional. A power that ordinary people could master through sheer effort, one that amplified the flesh in an instant — that alone was enough to count as a kind of demonic-fiend Corporeal Transformation, a mortal's own metamorphosis.
Kobe Hikaru couldn't be certain whether the Breathing Style would work for him at all.
But that was no reason not to try.
It was, at least, more within reach than Kikyo's pure-qi spiritual power, which lay entirely beyond him for now.
And so, at this moment—
every movement Tsugikuni Yoriichi made, every shift in the rhythm of his breath, the depth and pace of his chest's expansion, the path the qi traced through his body—
all of it, in that moment, was caught by his demon eyes, sharpened through the Sharp-Eye Mutation.
Once.
He'd watched it only once.
And already, he had committed the fundamentals of the Breath of the Sun to memory.
____
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