The next morning, under the pale light of dawn, Tachibana Kyūjō was already awake—earlier than usual.

His footsteps echoed softly across the cobblestone path of the Demon Slayer Corps headquarters, starting a routine that used to feel like second nature: morning training.

A slow jog. Nothing more.

But even that didn't last long.

Kyūjō stopped mid-stride, hunched over, struggling to breathe.

Each gasp burned like fire in his chest.

Though his body still bore the foundation of years of intense sword training and Thunder Breathing—strength forged through blood, pain, and sheer will—his internal organs told a different story.

His right lung was all but useless.

Just a little too much movement, and oxygen slipped away like water through his fingers.

His hands went numb. His legs buckled. The world began to spin.

If this kept up…

His body would rot from within, slowly, painfully.

"Why... why did it have to be my lung...?"

"Why couldn't it have been an arm or a leg…?"

Kyūjō stumbled to the side of the path, collapsing into a crouch, hands braced against his knees, wheezing in labored breaths.

Each one sounded like it came from someone at death's door—rasping, broken, agonizing to hear.

His body screamed at him to stop.

But his heart screamed louder.

He knew the truth.

Because of him, this world might soon drown in darkness.

That was why…

He had no right to stop now.

Recovering wasn't enough.

He had to become stronger than ever before.

Strong enough to defeat Muzan. Strong enough to surpass Kokushibō.

"Breathing…"

Teeth clenched, Kyūjō began forcing his lungs to fall into rhythm, trying to call forth the familiar pulse of Thunder Breathing's first form—something that had always been a part of him.

But the moment he tried—

Agony pierced through his chest like a blade from the inside.

The world around him turned black.

And his body hit the ground.

—

"Kyūjō-sama!!"

Maekawa Hirosuke sprinted through the corridors, shouting as he neared the residence of the Ubuyashiki family.

"Oyakata-sama! Kyūjō-sama collapsed—he's in critical condition!"

"Lady Tamayo is performing emergency treatment right now!"

Ubuyashiki Kagaya stepped out of his room with his usual composure, though a faint pallor touched his skin.

"What happened?" he asked calmly but quickly.

Hirosuke lowered his head, his voice tight with guilt.

"This morning... some of the others found Kyūjō-sama trying to exercise near the main road."

"Not long after that… he passed out."

Kagaya's eyes narrowed slightly.

He understood.

Kyūjō must have realized everything.

Kagaya sighed softly, a hand resting on the side of his robe.

He had expected this day to come. Just not this soon.

—

When Tachibana Kyūjō opened his eyes, a familiar light greeted him from above.

That ceiling… that bed…

It all felt like déjà vu.

He was back again.

A bitter smile tugged at his lips.

"This really is the last place I ever wanted to return to."

Beside him, Tamayo finally let out a quiet sigh of relief.

"...You really pushed yourself too far, Kyūjō-dono."

Her voice carried the tone of an older sister scolding a reckless sibling—gentle, but full of worry.

"Should I assume everything I told you as a doctor just went in one ear and out the other?"

"Let me make it perfectly clear—you are not allowed to use any form of Breathing Technique."

"Your lungs are far too damaged. They can't even handle light activity, let alone combat."

"If you had collapsed just a little farther from this facility… I'd be preparing a funeral, not treatment."

Kyūjō closed his eyes again.

His jaw tensed.

He knew all of this. And yet… he'd done it anyway.

Because what choice did he have?

If he couldn't use Thunder Breathing… then how could he atone?

How could he repay the lives that would surely be lost because of the mistakes he'd made?

Because of the future he'd shattered?

"Kyūjō."

The soft voice of Kagaya Ubuyashiki reached him from the side of the bed.

"You've figured it out, haven't you?"

Kyūjō didn't open his eyes.

He simply nodded.

Kagaya smiled quietly, then continued with a tone that was warm, yet firm.

"Kyūjō… do you believe we secretly resent you?"

"That we blame you for failing to kill Kokushibō… for allowing the rise of a new Demon King?"

"And because you think you can't fix what's happened… you've chosen to punish yourself instead?"

"If so… then you're underestimating us."

"You're underestimating the Demon Slayer Corps. You're underestimating me, Ubuyashiki Kagaya."

"And most of all—you're underestimating yourself."

His voice grew sharper.

Stronger.

"Do you know what the Demon Slayer Corps really is?"

"Do you know what it means to be part of the Ubuyashiki bloodline?"

"For over a thousand years, we've fought demons in mortal bodies!"

"Not with fleeting power, but with unwavering resolve!"

"Even if one generation fails to destroy Muzan, the will to fight is passed down—again and again!"

"Even when we lost all of our Hashira… and the Corps was on the brink of collapse…"

"The swordsmen who remained stood tall!"

"They never gave up!"

"If everyone thought the way you do now, we would've disappeared from history long ago."

"And the world would belong to the demons."

Kyūjō's eyes slowly opened.

He looked up at Kagaya, expression conflicted.

He knew Kagaya was right.

But… his circumstances were different.

Kyūjō wasn't born in this world.

He knew what was supposed to happen.

He knew this generation was meant to bring victory—that Muzan would fall, and the era of demons would end.

But now…

Because of him…

Because he interfered…

That future had changed.

Will they still win?

If so… how long will it take?

How many more swordsmen and innocents will die in the meantime?

The weight of it all bore down on his chest.

So many lives.

So much blood.

So many regrets.

Maybe this…

Was how Yoriichi Tsugikuni once felt, when he failed to slay Muzan.

Noticing the light fading from Kyūjō's eyes again, Kagaya took a breath and asked gently:

"Kyūjō… do you know when Breathing Techniques were first developed?"

"Around three hundred years ago. During the Sengoku Era."

"Then what about before that? What did the swordsmen of the Corps do before those techniques existed?"

"They still fought."

"Kyūjō… I'm not saying Breathing isn't important."

"But never forget…"

"It's not the technique that makes someone strong."

"It's the human who wields it."

"Yoriichi created those styles from nothing."

"If he could forge strength from the void—then why can't you?"

"Why not discover a new path—one that belongs to you and no one else?"

His words hit Kyūjō like a hammer to the chest.

Yes.

The true strength had never been in the forms or the breathing.

It was in the will of the one who wielded them.

And he—Tachibana Kyūjō—was the only human in this world…

…who carried the wisdom and experience of two entire worlds in his mind.

If he could combine what he'd learned from both…

If he could truly fuse those teachings…

Then surely—there had to be another way forward.

Not the Thunder Breathing of Zenitsu.

Not the Sun Breathing of Yoriichi.

Not a style born from lineage or legacy.

But a power that belonged to him, and him alone.

A new strength.

Forged from two worlds.

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