Half a day later, Rengoku Jinjuro crouched on the ground, hands braced on his knees, gasping for breath.
His face had flushed a deep red, sweat running down his forehead and dripping onto the flagstones with a soft patter, his chest as if someone had crammed a ball of fire into it — hot and stifling.
Another failure.
He could just barely manage the fundamentals of the Breath of the Sun that Tsugikuni Yoriichi had taught him — but he could only sustain it for about twenty breaths.
After the twentieth, his lungs felt ready to burst, forcing him to stop.
"No good. Still no good."
Panting, brow furrowed, he thumped his own chest with a rough, calloused hand.
The core of the Breath of the Sun was folding the sun's heat into the breathing cycle — but that fusion demanded an extraordinarily high tolerance from the body itself.
Body temperature spiked, blood raced, the heart's load surged — an ordinary body simply couldn't withstand it.
Yoriichi could do it because he was born for it.
His Transparent World gave him absolute command over his own body's condition — the width of every blood vessel, the tension of every muscle, all of it under his perfect control.
But Rengoku Jinjuro had no such gift.
All he had was the body he'd built up over a lifetime of training — strong by ordinary standards, but nowhere near enough for brute-force practice.
"Jinjuro."
Yoriichi crouched beside him, his deep-red eyes calm as he studied him. "The Breath of the Sun... might not suit you."
It was blunt.
But that was simply how Yoriichi was — he never spoke false words.
Rengoku Jinjuro froze for a moment.
"Not... suit me?"
"Every body is different."
Yoriichi rose, resting his Sun Blade on his shoulder. "I think the Breath of the Sun is the sun itself. There's only one sun — but the light it casts takes on different colors depending on where it falls."
"You don't need to learn the sun."
"You need to find your own light."
Rengoku Jinjuro fell silent.
A light of his own.
He looked down at his hands — calloused, scarred with old wounds.
Something came to him.
Fire.
His hands had gripped a torch countless times, tracking vengeful Demons through mountain forests in the dead of night — the torch had been his only light.
Flame. Burning.
And—
Blaze.
"Blaze..."
He murmured the single word.
Wasn't his own surname, Rengoku, itself just another face of that blaze? It was, after all, his family's inheritance.
Yoriichi glanced at him and smiled.
He nodded in encouragement. "Try it."
...
Across the courtyard, Kobe Hikaru had stopped watching them. He simply closed his eyes, sitting cross-legged on the stone platform.
The Sun Blade still lay across his knees.
In just a moment, its favourability had crept from 16 to 18.
Not fast, but not especially slow either.
Even though the sunlight energy within the Sun Blade refused his yokai aura — like two magnets of matching poles, the closer they drew, the harder they pushed apart.
But the yokai fire within him would, on contact with the Sun Blade, occasionally spark a moment of resonance — brief, fleeting, gone in an instant.
In that instant of resonance, the sunlight energy would begin to accept him, briefly mistaking him for one of its own kind.
He was exploiting these scattered windows of resonance, seeping in bit by bit.
Like water wearing away stone.
But his attention wasn't entirely on the Sun Blade just then.
He was also turning over something else at the same time — the full structure of Tsugikuni Yoriichi's Breath of the Sun, which he'd committed to memory in a single glance.
Remembering it and being able to use it were two different things.
Because his lungs were dead.
As an oni warrior, his body had already died at the very moment he crossed over.
It had come back afterward through the system's revival, driven by yokai aura, brought to life gradually through change after change — but that 'life' had grown from the outside in.
At least for now, most of his body was still dead.
Only the blood was changing, only the bones could grow.
Beyond that, the living heart and kidney were only projections of his Asura Mutation.
The lungs, the organ responsible for breath, remained dead.
He didn't need to breathe. Every breath he took was only an illusion mimicked by yokai aura — air entered the lungs and was expelled again, but the oxygen exchange in between never actually happened.
So there was no question of him learning the Breath of the Sun.
It was a technique built on the function of a living lung, requiring real gas exchange, requiring shifts in blood-oxygen levels to drive the body's function beyond its limits.
But—
What if he didn't take the path of the Breath of the Sun at all?
The core of the Breath of the Sun was the sun — the sun belonged to yang, to fire, to life.
That was Yoriichi's path, the path of the living.
But he was yokai, a Demon in his own right, and he hadn't truly come back to life.
The Breath of the Sun shone upon all things, granting power to the living — without question, a breath of the heavens.
He didn't belong to the heavens.
He belonged underground.
In the crack between Yomi and the world of the living, at the border between death and life.
For something that had already died once to imitate the sun's breath was like climbing a tree to catch fish — the wrong method entirely.
But... what if, instead of borrowing light from the heavens above, he drew qi from the ground beneath his feet — from Yomi itself, in his imagination?
Yomi in place of the sun, yokai aura in place of air, the pulse of the dead in place of the breath of the living.
The Breath of the Sun was the living breathing in the sun above.
Then he would breathe the Yomi beneath his feet.
...The idea had taken shape.
Kobe Hikaru opened his eyes. In his crimson oni eyes, the purple markings and streaks of orange light flared up together.
He raised a hand, palm turned upward.
Then he drew a breath.
Not with his lungs — with his yokai aura. The aura across his skin contracted sharply, drawing in the turbid qi of heaven and earth that hung diffuse in the surrounding air.
The turbid qi passed through his nose and mouth into those dead lung lobes.
The lobes themselves didn't move. But the yokai aura did.
The turbid qi spun and gathered within the lungs' remaining structure, coiling and circling until it formed a tiny vortex.
The vortex turned.
Slow, heavy, carrying the chill and density of heaven and earth's turbid qi — not expanding outward like the sun's heat, but sinking downward as if pulled by the gravity of the legendary road to Yomi, dragging everything toward some deeper place.
There was none of the Breath of the Sun's blazing, luminous expansion.
Only — sinking.
Sinking beneath the earth, sinking into the realm of the dead, sinking into that eternal darkness to which all things must eventually return.
As if a door to Yomi had opened somewhere inside him.
The turbid qi he'd drawn in circled once through his lungs before the yokai aura pushed it out again — but by the moment it was expelled, it was no longer the same turbid qi at all.
It had been filtered.
Refined. Purified.
It had become a thicker, purer yokai aura, better suited for a yokai to absorb, fit to power his yokai frame.
If the Breath of the Sun was the sun's gift to the living — shining on all things, making them grow—
then Kobe Hikaru's breath was more like Yomi's gift to the dead — settling all things, returning them to their roots.
His lungs didn't breathe air, yet they could filter and purify the turbid qi of heaven and earth and send it back out — just as the road to Yomi, though a path of death, was also the starting point for the cycle of all things.
One in the heavens, one beneath the earth.
One granting life, the other governing death.
The Breath of the Sun ends in light.
The Demon's Breath ends in stillness.
Yoriichi's Transparent World, innate to him from birth, let him command the sun's breath perfectly — because he was a living man, a chosen son favored by sunlight.
But Kobe Hikaru had already died once. His lungs were dead, most of his body was dead — which was precisely why the breath of Yomi was the breath that truly belonged to him.
The living breathe sunlight.
The dead Demon breathes Yomi.
Each walks his own road, each has his own pinnacle.
This was... the Demon's breath.
The Demon's Breath!
Not the breathing of air — but the breathing of Yomi!
The dead lungs as furnace, the turbid qi as raw material, the yokai aura as the transforming agent.
Intake, refinement, circulation.
And in the instant that first breath of the Demon was completed—
deep within his chest, those long-silent, dead lung lobes flickered, just once.
The briefest instant.
A dim light, somewhere between black and purple, abruptly took shape where his lungs sat — as if a gate to Yomi had cracked open between the two withered lobes.
Then—
it went out again.
One flicker, and it was gone.
Something was still missing.
Missing...
[Sun Blade (Favourability: 32; First Talent Unlocked — 'Slay Demons', Bonus Damage against Demons); the wish that gave it birth: 'Slay Demons']
What was missing was the talent that came at full favourability.
Kobe Hikaru understood.
The Sun Blade was only a half-yokai weapon, not a yokai weapon in its complete form — even the talent granted by full favourability alone wasn't enough to let him complete another Asura-transformation projection outright.
But combined with his grasp of the Demon's Breath, it was enough.
The Sun Blade and the Demon's Breath reinforced each other.
Favourability leapt straight from 18 to 32 — the resonance was overwhelming.
But it still wasn't enough.
Simple feeding through conversation alone wouldn't be enough to bring it to full favourability any faster.
What it needed was — to slay a Demon.
The very reason the Sun Blade had been born was to sever the undying nature of vengeful Demons.
If he didn't fulfill the reason this blade existed, it would never truly accept him.
That wasn't something pouring in yokai aura could fix, nor something sweet words could talk around. What it wanted was action.
That brief flicker of Yomi-light a moment ago had already, without question, pointed the way.
The form of an Asura's lung existed — it simply needed the right conditions to wake it.
And at the same time—
the thin, dim, cold mist that had leaked out the instant the Demon's Breath took shape — brief as it was — had already been enough to bring about another change.
He looked down at the Sun Blade resting before his knees.
The blade's color had changed.
From its original pale-orange sheen, it had shifted into a deep, murky hue somewhere between black and purple.
Like... the color of Yomi.
This, too, was the origin of the color-shifting blade's name.
Black shot through with purple, purple sunk into black — a color the sun could never reach.
A color only something that had already died once could ever take on.
"From now on, I'll call you... Yomikiri."
Sun Blade — Yomikiri.
Also known as: Undying-Slayer.
A fitting counterpart to Onikiri and Raikiri.
Out on the corridor—
Rengoku Jinjuro was trying to fold the concept of blaze into his breath. He had an idea now, but he clearly hadn't found the way in yet.
The veins on the young man's forehead bulged, his face flushed red as a boiled shrimp.
Then, from the corner of his eye, he caught the fleeting dark mist over the stone platform across the courtyard, and the sudden shift in the Sun Blade's color.
—and, in the yokai's half-opened eyes, a dim, fathomless glow had risen within the crimson oni eyes, like the depths of a Yomi abyss.
Rengoku Jinjuro's movements stopped.
His mouth opened, then closed again, and he turned to look at Yoriichi.
Yoriichi was already looking that way too.
For the first time, true surprise showed in those deep-red eyes.
"He..."
Rengoku Jinjuro's voice carried a note of astonishment. "Master Hikaru... has he learned it?"
Yoriichi didn't answer.
But his Transparent World eyes told him that something was indeed changing within that yokai gentleman.
The change seemed incomplete, as if it had only just begun — yet it already looked deeper and more complex than his own Breath of the Sun.
It wasn't merely a breathing method.
It was a metamorphosis that used breath as a bridge to reshape one's own internal circulation.
"Master Hikaru is a remarkable, extraordinary yokai."
Yoriichi said it under his breath.
He offered nothing more.
On the corridor, Rengoku Jinjuro crouched, looking first at Yoriichi, then at Kobe Hikaru, and finally down at his own hands, still fumbling for the way in.
After a long moment, he forced out a single line.
"What am I even doing?"
The man had only seen the breathing technique half a day ago, and already he'd created one of his own.
And here he was, still coughing.
And that one over there was a yokai, no less.
A yokai... sharper than any human.
Jinjuro blew out a breath, clenched his fists, and pushed himself back up, utterly unwilling to accept defeat.
After all, stubborn refusal to accept defeat was precisely the fuel the Rengoku family did best.
"Again!"
He shouted it at Yoriichi, then drew a deep breath—
and coughed again.
Yoriichi could only sigh, and even Kobe Hikaru cracked a smile.
Meanwhile, elsewhere in the rear courtyard of Ubuyashiki Mansion—
Cho sat by the veranda, a set of medicine-mixing tools laid out before her, but the pestle in her hand had gone still. Her gaze lifted, as if trying to see clear across the courtyard to the other side.
It stayed there a long while.
Long enough that another figure, walking up beside her, gave her a light flick on the head.
"What are you staring at?"
The braided-hair girl among the seven Hashira stood by the veranda, a smile on her face.
"Sister, you're back?"
The braided-hair girl of the seven Hashira was, without question, Cho's own sister — real sisters, born of the same blood. The elder had risen to Hashira rank on sheer talent, while the younger was only an untalented Kakushi member; the gap between them was hardly small, yet the two seemed no less close for it.
The braided-hair girl smiled gently. "I've been watching you watch for a whole quarter hour, you know?"
"I was thinking about something."
"Thinking about what?"
"Thinking about—"
Cho turned the pestle over once, and finally settled on an answer that sounded reasonable enough. "Thinking about what I saw — the iron flowing down off the mountain by itself."
The braided-hair girl fell silent for a moment.
She'd only just returned from patrol that day, and had already heard the story from others—
seventy-two Sun Blades, finished in a single day, every piece of ore feeding itself into the forge while the smiths simply stood by and watched.
Her first reaction, naturally, had been that it wasn't possible.
As a Hashira, she'd been to the Swordsmith Village more times than she could count, and she knew all too well how difficult forging a Sun Blade truly was.
But after hearing the whole account and seeing the storeroom stacked with seventy ownerless Sun Blades, all that was left in her was silence.
Still—
"What's there to think about?"
The braided-hair girl tapped her sister's head. "That gentleman is a guest even our lord holds in the highest regard."
She said it as if it meant nothing to her.
But Cho knew her sister was lying. After all, for a Corps swordsman, one more Sun Blade meant one more chance to slay a Demon — that mattered enormously.
She didn't call her out on it.
The two sisters sat by the veranda without speaking for a while, the courtyard breeze carrying the wisteria's scent to mingle around them, laced with an odd sweetness.
"Sister."
After a moment, Cho spoke again, her voice a little lower than before. "Do you think Master Kobe Hikaru can really help us kill the progenitor of the Demons...?"
"Maybe he can, maybe he can't. Who could really say?"
The braided-hair girl tilted her eyes without pausing, her answer brisk and clear. "But I think he might be the strangest, and the most distinguished, guest the Demon Slayer Corps has ever had."
"...Mm."
Cho glanced in that direction, wholeheartedly agreeing.
It had only been two days, but the yokai gentleman had left a real impression on the girl.
The braided-hair girl left soon after.
Cho tucked the thought away and went back to turning her pestle.
The courtyard breeze stirred the wisteria clusters gently, and two or three petals drifted down onto the ground beside the stone platform.
Then — they stopped.
They didn't roll any further, as if something had gently pressed them down.
In that same moment, the breeze also carried over the sounds from the courtyard next door.
Cho stared at the two or three petals for a while, listening to that laughter, and found herself thinking again of that pair of crimson demon-eyes.
and that figure who seemed so cold and severe, yet was, underneath it all, gentle toward everything in the world.
By the time she came back to herself—
she found the medicine in her hands had already been ground to powder. She stared at the little pile, touched the Sun Blade at her waist, and let out a silent sigh.
She decided that next time, she'd keep at least two courtyards' distance before rubbernecking.
Mixing medicine, of all things, was no time to lose focus... She couldn't disappoint this blade. She needed to work harder, Cho...
Still, come to think of it—
"Could I learn a breathing technique too, I wonder?"
Having overheard the conversation from the courtyard next door, Cho found herself thinking — if this were before, she never would have. But now, the Sun Blade at her waist had planted that longing in her.
She wanted—
"You could try."
The voice came out of nowhere.
Cho's focus slipped again — and this time, when she snapped back, she found herself looking straight up into a pair of demon-eyes hovering right above her, appearing as if out of thin air.
Then she screamed.
____
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