Chapter 10 – Kagaya Ubayashiki
Two days passed in peaceful quiet.
Hikaru continued his days just like before—reading, learning, living at his own pace.
But now, there was one more thing added to his daily rhythm.
Writing.
Each morning, after reading medical texts and practicing mindfulness techniques, Hikaru would sit cross-legged before a low table, brush in hand, and begin transcribing everything he knew.
Not just knowledge from books.
But his own martial art.
[Nameless Martial Art (F+)]—the technique born from countless hours of training, hunting, and surviving—was now being organized into text, refined stroke by stroke.
What started as a chaotic blend of instincts and improvisation had become something more: a structured combat form with its own rhythm, logic, and application.
By now, it had even surpassed one of the official Breathing Techniques—Mist Breathing—in depth and clarity.
If a rank of "F" represented an extraordinary human, then "F+" had already nudged beyond the limits of the ordinary.
Still… Hikaru knew.
This was only the beginning.
If he nurtured this as a foundation, it might one day blossom into something akin to Uncrowned Martial Art—the legendary style once wielded by Karna, the demigod hero of Indian mythology.
Just as his passive skill [Calm Mind] had the potential to evolve into Eye of the Mind, a technique once possessed by the fabled swordsman Sasaki Kojiro…
It was only speculation, of course.
Because martial arts weren't just theory. They were a manifestation of the self—dependent on body, will, instinct, and lived experience.
And at the moment, Hikaru's physical attributes were still modest. Strength, Endurance, Agility—all remained at the F tier.
He couldn't yet bring out the full potential of his martial art.
But that didn't trouble him.
There was no need to rush.
He would move forward, one step at a time.
— — —
On the second day, the sun blazed high outside the window.
Summer had come.
The scent of spring—of blooming wisteria—had faded from the mansion grounds. In its place, the warm fragrance of sunlit soil and the faint hum of insects hinted at the change in season.
But within the Butterfly Mansion, Hikaru's heart remained still.
He sat calmly in his room, brush gliding across parchment as he penned the final line of his work.
When he finally lifted the brush and blew gently on the ink, he let out a long breath and looked up—
Shinobu Kocho was standing by the door, as if she'd been there for a while.
Her soft smile didn't falter.
"My, my… you really aren't in a hurry, are you?"
"There's no reason to be," Hikaru said, setting down the brush. "You wouldn't ignore me now, would you?"
A breeze passed through the hallway.
Shinobu's long, dark hair shimmered with a hint of blue at the tips, catching the light like butterfly wings.
She didn't deny it.
Couldn't deny it.
"…Oyakata-sama would like to see you," she said.
Hikaru didn't seem surprised.
He carefully picked up the manuscript he had just finished and let the ink dry completely before standing.
No tension.
No fear.
"Then let's go," he said simply.
Shinobu nodded, falling into step beside him.
— — —
They returned to the same place as before—the main courtyard of the Demon Slayer Corps headquarters.
But this time… it was different.
When Hikaru first came here, only two attendants in black and white had stood waiting.
Now, at the center of the room…
Sat a man.
"Oyakata-sama," Shinobu said, bowing deeply.
"You don't need to be so formal," came a gentle voice, so calm it could soothe any storm.
The tall, slender figure turned slowly to face them.
His face was… not handsome.
In fact, it could only be described as tragic.
From the bridge of his nose upward, his skin was marred with deep, bark-like purple scars—like the surface of a tree withered by time. The parts of his face that remained unscarred were pale and delicate, like a bloom that had outlived its season.
And yet—
There was no fear.
Instead, a stillness emanated from him.
An aura of quiet strength.
His voice, soft and light, brushed gently against the heart, like a spring wind caressing your cheeks.
——Like a saint.
That was the first impression Hikaru had of this man.
But he knew better than to let that lull him into comfort.
——[Calm Mind], activate.
Hikaru bowed respectfully.
"My name is Kagaya Ubuyashiki," the man said. His eyes, despite the scars, held a warm glow. "But you may call me simply Kagaya."
"I've heard about you from Shinobu," he continued. "She tells me… you've completed a technique, born from your time training and hunting?"
No preamble.
Straight to the point.
But still, his tone was courteous—never imposing.
"Yes." Hikaru nodded and presented the scroll in his hands.
One of the attendants in white stepped forward, received the manuscript from him, and brought it to Kagaya's side.
The leader of the Demon Slayer Corps gently ran his hand over the paper.
"Hmm…"
"This is remarkable. And unlike the Breathing Techniques… it seems anyone can learn it?"
Breathing Techniques relied on momentary bursts of power—on pushing the body beyond its limits through enhanced oxygen flow.
But Hikaru's technique—[Nameless Martial Art]—was different.
It focused on efficiency. Control. A complete mastery of one's natural movement, perception, and rhythm.
Even those who couldn't use a Breathing Style… could learn this.
And those who could?
Would find no conflict.
Only synergy.
Just as Hikaru had once told Giyu Tomioka:
This technique had the potential to strengthen the entire Demon Slayer Corps.
Not through dramatic leaps… but through steady, universal growth.
"I see…" Kagaya murmured.
Then he looked up.
"What would you like in return?"
The question wasn't a challenge.
There was no pressure in his voice.
No weight of expectation.
Only kindness.
A leader who didn't wield authority to bind—but to nurture.
For many, such a moment might feel overwhelming.
But not for Hikaru.
He had made his decision long ago.
"All I want… is more opportunities to grow stronger," he said.
"And with that strength—I'll destroy every last demon."
Simple words.
But his conviction was real.
— — —
Kagaya fell silent for a moment.
He had seen many warriors in his time.
But this boy—this young man who had created something powerful and shared it so freely—
Was a rare gem.
Someone who did not need to be commanded.
Only trusted.
"…Starting today," Kagaya said softly, "you will be recognized as an A-Class member of the Demon Slayer Corps."
"And more than that—"
"You may choose any Hashira to be your personal mentor."
A-Class.
A rank typically awarded to those who had slain over fifty demons.
Hikaru had no such record.
But this contribution…
Surpassed even those who had shed blood on the frontlines.
If not for his physical stats still sitting in the F tier, he might've already qualified to be a Hashira himself.
And in the Demon Slayer Corps, there was no cap on the number of Hashira.
For Hikaru, this recognition was more than just a badge.
It was permission.
Permission to walk alongside legends.
To learn from the best.
To see the deepest essence of the Breathing Techniques—
And fuse them with his own path.
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