It wasn't until Tamayo herself confirmed the results that Tachibana Kyūjō finally allowed himself to breathe easy—literally and figuratively.

"Then... is there a clear difference between this Body Breathing technique and normal lung-based breathing?" Kyūjō asked, his curiosity flaring like a spark ready to ignite.

Tamayo furrowed her brow slightly, contemplating her answer in silence before speaking.

"For now, there's no drastic difference—except for one key point."

"Since the oxygen is absorbed directly into the capillaries without going through the lungs, the efficiency is far higher."

She paused, then added with a more somber tone:

"But... this Body Breathing you've discovered—"

"It's far too complex. No ordinary person could ever master it."

As a doctor, saving lives was the very core of Tamayo's soul.

So when she realized the enormous potential of this technique—something that could theoretically cure even the most severe lung diseases—but also realized that it couldn't be taught or spread easily...

Her heart ached with quiet regret.

— — —

The Next Morning

Word of Kyūjō's breakthrough reached the ears of Kagaya Ubuyashiki, head of the Demon Slayer Corps.

Despite the usual air of mystery that clung to the young master like morning mist, this time Kagaya didn't wait for ceremony or timing. At the break of dawn, he was already at Kyūjō's home.

But to his surprise...

Kyūjō was up first.

Out in the courtyard, under the pale golden rays of morning sun, the young swordsman was already swinging his Nichirin Blade with terrifying precision.

Each slash tore through the air like thunder cleaving the sky.

There was no wasted movement. No hesitation. Only sharp, fluid execution.

Kagaya froze at the entrance, his steps halted by sheer disbelief.

The man before him... wasn't the same Kyūjō he once trained taijiquan with—two frail men, both struggling with their fragile health, trying to grasp at meaning between breathless nights and trembling limbs.

No.

This Kyūjō was something else entirely.

"Unbelievable..."

The words slipped from Kagaya's lips, unbidden.

Kyūjō, having sensed his presence, turned with a bright smile and wiped the sweat from his brow.

"Morning, Oyakata-sama. You're up late today."

"Didn't sleep well last night?"

Kagaya inhaled deeply, trying to suppress the mix of frustration and amazement welling up inside him.

"You little... Still playing innocent after stealing all the good fortune?"

He crossed his arms, feigning indignation.

"Remind me—who was it that couldn't even get out of bed not too long ago?"

"Who looked like they'd given up on life entirely?"

"And now you're standing here swinging a blade like a damn Pillar?!"

Kyūjō winced.

Even with his thick skin, he couldn't help but flush with embarrassment.

Without another word, he rushed over and cupped Kagaya's mouth with both hands, his voice suddenly soft.

"Kagaya... you're my brother, yeah?"

"Please. I beg you. Stop talking... right now..."

Kagaya's expression softened into a smug grin. He gave a satisfied nod.

Only then did Kyūjō remove his hands.

They stared at each other in silence for a beat—

And then burst into laughter.

No words. Just raw, unspoken joy. A bond deeper than blood.

Despite being head of a noble family, Kagaya was still just a teenager.

And though he'd been born with wisdom far beyond his years... deep down, he was still human. Still a boy who longed for genuine companionship—someone who didn't look at him like a divine figure wrapped in silk and burdened by fate.

Kyūjō had never treated him with reverence.

No kneeling. No flowery praise.

Just quiet, honest respect—and a heart that saw him as Kagaya, not the master of the Corps.

That's why they could laugh together like this.

Kyūjō slung an arm over his friend's shoulder and looked up at the morning sky, a soft smile tugging at his lips.

"Hey, Kagaya... do you believe me if I say I can read a person's face?"

Kagaya didn't even blink.

"Nope."

He deadpanned.

"And if that's true, then I'm the Emperor of Japan. You believe that?"

"Pfft—!"

Kyūjō doubled over in laughter, clutching his stomach.

A few seconds later, he exhaled, his face now calm—serious, even.

"But I can read faces."

"And I can tell, just by looking at yours... you're going to live a long life."

"You'll outlive the curse passed down by your family."

Kagaya froze. His eyes met Kyūjō's, searching.

And then... he nodded.

"Then I believe you."

"Because that's the best thing I've heard all day."

— — —

Three Days Later

Far from the Corps Headquarters, a lone figure moved along a narrow mountain path.

His blade—a black Nichirin katana—was slung across his back.

In his hand, a familiar, battered iron pot swayed gently with each step.

"Mount Kumotori... That's where the Kamado family used to live."

"Which means I'm heading east. Toward the Odōmu region."

Tachibana Kyūjō had officially left the Demon Slayer Corps HQ.

His journey as a demon slayer had begun anew.

And this time... he knew the road ahead would be even harsher than before.

But that didn't matter.

If he failed—he would die. Simple as that.

A true swordsman does not take their final breath on a bed of pillows.

He had awakened his Demon Slayer Mark, a power that burned through life itself. His time was limited—less than three years, if he stayed holed up in the safety of the Corps, doing nothing but research and slow training.

That would never be enough.

He needed two things.

First: To find Kamado Tanjūrō, father of Tanjiro—the only living person who had ever truly grasped the secrets of Sun Breathing.

Second: To face real demons in real battle. To forge instinct, sharpen spirit, and lay the foundation for a new breathing style—one that belonged to him alone.

Body Breathing.

For reasons he couldn't quite explain... Kyūjō believed with absolute certainty—

That hidden within the mystery of Sun Breathing lay the key.

The key to a new path.

A breathing style born of the body.

Powered by the body.

And wielded for the body.

Because in this world...

Only Sun Breathing could ever be called the perfect style.

All other forms—Water, Flame, Wind, Thunder, Mist...

They were but echoes. Shadows.

And now, Kyūjō's task was clear.

To create the one technique that wasn't a shadow of another.

A breathing style crafted not from tradition... but from life itself.

— — —

Author's Note:

Today I received my first negative review.

To be honest, I've poured a lot of time and heart into this story. Maybe the pacing near the end wasn't as polished as it should've been. But I promise—I'll finish this Kimetsu no Yaiba arc properly.

If any part of the story feels off or makes you uncomfortable, please leave a direct comment on that chapter. I read every single one. And if it makes sense, I'll revise it.

Reviews on the main page affect this story's performance a lot...

And as a writer—I need to eat too, right?

So I ask for your continued support.

Thank you for walking this path with me.

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