Chapter 40 – The Strongest Demon
Tamayo once had a personal connection with Oyakata-sama—Kagaya Ubuyashiki, the leader of the Demon Slayer Corps.
In this world, only two demons existed who had never consumed a single human: Tamayo and Yushiro.
And the only reason they could live that way was thanks to Tamayo's unparalleled medical expertise—knowledge she had refined over centuries.
Her true talent lay in medicine.
That was what caught Muzan Kibutsuji's attention long ago. He had offered her his blood, turning her into a demon and forcing her to remain at his side for years.
But despite that, Tamayo had accomplished the impossible—she broke free of Muzan's direct control and shattered the blood curse that should've bound her.
Even though she hadn't yet succeeded in turning demons back into humans, that alone was already a medical miracle.
No wonder the Demon Slayer Corps held her in such high regard.
In fact, for centuries, Tamayo and the Ubuyashiki family had secretly exchanged letters—personal letters. Their relationship wasn't just cooperation… it was a true friendship.
Hikaru knew all this.
That was why—before he left—he made sure to deliver Oyakata-sama's message, to ease Tamayo's heart and let her know he had come not as an enemy.
He wanted her to understand… he meant no harm.
But—
Whatever she thought afterward… whether she misunderstood, overthought it, or not… it didn't matter.
Hikaru had already walked away.
— — —
He kept walking.
Moving forward, step by step.
Tamayo's words still echoed in his mind. Just a single sentence. But that single line had come from the only living person who had ever seen Yoriichi Tsugikuni in the flesh.
To him, those words were priceless.
Transparent World.
A high-level concept—one he had heard of in stories and records throughout his travels. He didn't fully grasp the details yet, but he was certain it was one of the ultimate peaks of all Breathing techniques.
For now, all he could do… was reflect on its meaning.
He would have to discover the path on his own.
"To reflect everything within yourself… without clinging to anything. No ego. Pure transparency…"
Hikaru muttered to himself, deep in thought.
From time to time, he flipped through Tamayo's medical notebook.
It was thin—yet packed with knowledge. Each page condensed centuries of medical research.
It didn't directly make him a doctor, of course. But his understanding of the human body—and demonic biology—deepened with every line he read.
After leaving Tamayo's residence, Hikaru chose a different path—one that led away from Tokyo.
He returned to his journey.
Hunting demons. Strengthening himself.
Piecing together every experience into a clearer, sharper understanding of Void Breathing.
He wanted to build his own style.
From the ground up.
A step-by-step creation.
It wasn't easy.
But he understood this well: if you give up just because something is difficult, then you'll never accomplish anything.
"Void Breathing… the essence of void is emptiness. But at the same time… illusion."
"Nothingness… illusion… how do I connect that to reality?"
This was his biggest challenge.
So far, the only form he had mastered was Mirror Flower, Water Moon—a technique that manipulated light and vision to create illusions and hypnosis.
But it merely distorted perception—not reality itself.
That was what he was chasing now.
As he walked, he kept remembering the man who created and perfected the entire breathing system—Yoriichi Tsugikuni.
The one who was called a god by those who had seen him with their own eyes.
Hikaru recalled every description, every fragment, every image he had gathered.
And from them, he tried to unravel what remained—imitate it, study it, internalize it.
Step by step, he walked.
The sun dipped below the horizon.
The moon slowly climbed into the night sky.
And his journey carried him further from Tokyo.
Night fell.
Then—
A breeze brushed against his cheek.
Overhead, his Kasugai Crow let out a low, harsh cry. Its tone was different this time—uneasy. Anxious.
Hikaru narrowed his eyes.
"…This pressure…"
His brows furrowed slightly.
All around him, it was quiet. The night wind whispered through the tall grass. Leaves and blades danced under the moonlight like falling snow.
Everything seemed peaceful.
But within that silence… he felt something.
Ahead of him…
There was a presence.
Something strong.
He couldn't see it—but he could feel it.
At this point, Hikaru's combat instincts had reached an advanced stage. And when someone reaches that level, sometimes they can sense what isn't visible.
Call it—
Instinct.
It wasn't yet a technique.
But it was real.
And in the very next moment…
He realized.
Something… was waiting for him up ahead.
And it was powerful.
Far more powerful than anything he had faced so far.
Even the pressure it exuded—the sheer killing intent—felt sharper than what he'd sensed from Muzan himself.
Granted, he had never witnessed Muzan's full power.
But still…
This aura was on a different level.
That thought struck him like lightning—and instantly, Hikaru's body froze.
Then—
He turned.
Retreated.
He wasn't a fool.
And he definitely wasn't reckless.
Whatever was ahead… it was dangerous.
Even his crow—the messenger that rarely reacted—was showing signs of panic he had never seen before.
That wasn't a human.
It could only be a demon.
And without a doubt—
One of the Twelve Kizuki.
An Upper Moon.
Hikaru wasn't sure if this was fortune or misfortune.
Only six months into his journey, and he'd already run into several of the elite demons that even the Hashira rarely encountered.
But he understood his limits.
While he could handle Lower Moons with ease… Upper Moons were in a completely different league.
The gap between Lower and Upper wasn't just large.
It was absolute.
If someone knew how dangerous something was—and still chose to charge forward—that wasn't bravery.
That was idiocy.
So—
The moment Hikaru sensed the danger—
He turned back.
Without hesitation.
But just as he spun around to flee—
Something stopped him.
His legs froze.
His eyes widened.
The night wind intensified, sweeping across the landscape. Grass and leaves swirled like a snowy mist, blanketing the world.
The moon still hung in the sky—
But now, its color had turned blood red.
And in that crimson light—
A figure appeared.
Towering.
Draped in a long, flowing black cloak that billowed with the wind.
In his right hand, he held a long, dark-red katana.
And from the six eyes that glowed on his face—
A single kanji burned into view:
"Upper Moon One."
His gaze—cold.
Unmoving.
Locked directly onto Hikaru.
Hikaru's body went rigid.
He couldn't move.
It was him.
Upper Moon One.
Muzan Kibutsuji's strongest subordinate.
The most powerful demon—
Still alive in this world.
— — —
Author's Note:
PS – I'm really bad at naming techniques…
So if you guys have any suggestions for names for Void Breathing forms, feel free to drop them! Thanks a lot!
— — — — — — — — — — — — — — — —
📚 Want to read more chapters or get early access?
Join my Patreon here:
🔗 patreon.com/FaaanzKun
✅ Enjoy 35+ chapters ahead of WebNovel
✅ Get 1-2 new chapters every day exclusively on Patreon
📚 Want to read more chapters or get early access?
Join my Ko-Fi here:
🔗 ko-fi.com/faaanzkun
Join now and dive deeper into the story—weeks ahead of public release!
Thank you for your amazing support 💖
— — — — — — — — — — — — — — — —