A Flash of Inspiration

Night had fallen, and the Butterfly Mansion was quiet, with only a lone figure lying on the roof.

Kashu had once again dragged himself free from a violent rejection reaction. Every failure came with ringing ears, splitting headaches, blood flowing in reverse, and agonizing pain as though his heart and lungs were being torn apart.

If not for the powerful restorative ability of [Crystal of Stars], which could repair his injuries on its own, he would not dare play with several lives like this.

Kashu lay on the cool tiles, staring up at the vast starry sky with tightly furrowed brows.

"Tch. Was I too greedy after all?"

Trying to create an entirely new Breathing Style was a hundred times harder than he had first imagined.

The Demon Slayer Corps' five fundamental Breathing Styles: Water's endurance, Flame's intensity, Wind's ferocity, Thunder's speed, and Stone's steadfastness.

Each had its own focus, each its own strengths and weaknesses, yet he could not find a perfect rhythm that could fuse them all together.

The result of forcibly blending them was that even his powerful physique had nearly collapsed.

"Focusing on Wind Breathing and refining a style suited to me might be faster..."

Kashu murmured to himself. Thoughts of giving up spread like vines, only to be tightly strangled by the unwillingness deep within his heart.

He had never been one to settle for second best!

Just then, the faint sound of footsteps on roof tiles came from behind him.

Kashu turned his head and saw Tanjiro approaching carefully with a meal tray. Thick bandages still wrapped his body, making it obvious that his injuries had not yet healed.

"Mr. Kashu, Aoi said you did not come down for dinner, so I brought some up for you."

Kashu sat up and beckoned to him.

"You do not have to be so formal. Just call me Kashu. I'm only three years older than you."

But Tanjiro stubbornly shook his head, his expression turning serious.

"How could I? You saved our lives. Without you, Nezuko and I might already have..."

Kashu raised an eyebrow and cut off his explanation.

"How is your sister?"

At the mention of Nezuko, a smile immediately bloomed on Tanjiro's face, and his tone lightened.

"Thank you for asking. Nezuko has mostly recovered!"

"Is that so... Good."

Kashu nodded, an almost imperceptible gentleness slipping into his voice.

Tanjiro keenly caught that emotion and scratched his head curiously.

"I get the feeling that Mr. Kashu cares a lot about Nezuko?"

Kashu picked up a rice ball from the tray and took a bite, turning his gaze back toward the stars. His tone was calm.

"Probably because I have a younger sister too."

Tanjiro's eyes lit up. "Huh? Mr. Kashu has a sister too? Is she waiting for you to return in Europe?"

Kashu calmly shook his head, his voice utterly flat.

"No. She died in an explosion."

Tanjiro: (°Д°;)?!

The previously relaxed atmosphere froze. Even the night wind seemed to stop, leaving only the faint sound of Kashu chewing to echo across the roof.

Realizing that he had struck a painful nerve, Tanjiro hurriedly searched for another topic, his tone unusually stiff.

"Ah... r-right! I saw the Kakushi bringing in lots of boxes. Have you been busy with something special lately, Mr. Kashu?"

He quickly added, "Like me, I'm working hard on breathing training for Total Concentration: Constant!"

Total Concentration: Constant was the formal term for maintaining a Breathing Style around the clock.

Mastering this method allowed one to continuously strengthen one's physical abilities, and it was the most basic requirement for becoming a Hashira-level swordsman.

Kashu brushed the rice grains from his hands, took a sip from his teacup, and explained.

"Something similar to you. I'm trying to create a completely new Breathing Style."

"A new Breathing Style..."

Tanjiro fell into thought. The Demon Slayer Corps had existed for over a thousand years, and there had been no shortage of geniuses who created their own Breathing Styles.

His companion, Inosuke Hashibira, was one such person. Based on Wind Breathing, he had developed the wild Beast Breathing.

Then, memories of the desperate battle on Mount Natagumo surged into his mind.

At the brink of death, the kagura dance his father had taught him had somehow become a power capable of defeating his enemy. Its strength, far surpassing Water Breathing, still left him deeply confused.

Why could a dance meant to worship a god be used in battle?

He had intended to ask Shinobu Kocho, the Insect Hashira, after recovering, but now...

"Mr. Kashu."

A glint of inquiry flashed in Tanjiro's eyes as he spoke in a low voice.

"Have you ever heard of 'Hinokami Kagura: Dance'?"

"Hinokami Kagura: Dance?"

Kashu set down his teacup and rapidly searched through the vast archive provided by the Ubuyashiki clan in his mind, but ultimately shook his head.

"I do not remember it. From the name, it sounds like some kind of dance performed to worship a god?"

Tanjiro nodded vigorously. "You're right!"

"It is a kagura dance passed down through my family for generations, performed every winter as an offering to pray to the Fire God for safety."

"But when I was fighting Lower Rank Five, I remembered my father's teachings and somehow... somehow used it as a Breathing Style!"

Something inexplicably tightened in Kashu's chest, and his casual posture straightened slightly.

"A ritual dance passed down through generations can be used as a Breathing Style?"

This was far too interesting.

The Kamado Family not only had special constitutions that allowed them to quickly adapt to demon blood, but even their inherited dance was extraordinary?

A hazy flash of inspiration exploded in Kashu's mind, as though he had grasped some crucial clue.

He abruptly stood up, pulled a small crystal vial from inside his clothes, and tossed it to Tanjiro.

"Drink it, then show me the Hinokami Kagura: Dance."

"Ah? Yes!"

Tanjiro caught it instinctively. Though confusion showed on his face, he obediently pulled out the stopper and downed the liquid in one gulp.

The bitterness he had expected never came. Instead, it went down like sweet spring water, and warmth instantly spread through his entire body, followed by a strange tingling sensation.

A faint green glow flashed across Tanjiro's body and vanished. He clenched his fists in delight and sprang to his feet.

"My injuries... they're completely healed!? This is incredible!"

"Mm. The effect really is immediate."

Kashu observed from the side and nodded to himself.

Because he possessed the powerful restorative ability of [Crystal of Stars], this was the first time he had witnessed firsthand the effects of Orario's panacea.

This was a precious potion that could only be brewed by an alchemist who possessed the development ability [Mixing].

The restorative effects of panacea were remarkable. It was said that it could even drag dying adventurers back from death's door.

Seeing Tanjiro recover so completely in an instant, it was no wonder Loki had looked so pained when she handed the thing over to him.

"Um... Mr. Kashu, this medicine... is it very expensive?"

Tanjiro's excitement had now faded. He shook the empty vial in his hand, his voice dry as sun-cured charcoal.

Kashu raised an eyebrow and answered teasingly.

"It's all right. Just five hundred thousand a bottle. Someone gave it to me before I left, in case I needed to save my life."

"F-five hundred thousand!?"

Tanjiro looked as if he had been struck by lightning, instantly petrifying on the spot.

His family had made a living selling charcoal for generations. When had he ever seen an astronomical number like five hundred thousand?

"Th-this is far too precious, I..."

Kashu raised a hand to stop him, pointing toward the rehabilitation grounds behind the house.

"Instead of standing here worrying about the money, hurry up and show me your Hinokami Kagura: Dance."

"If it can really help me solve my current problem, then those five hundred thousand will have been more than worth it."

Tanjiro's gaze instantly became firm, and he nodded hard.

"I understand! Please follow me!"

Without further hesitation, he turned and ran toward the training ground below.

Under the night sky, an ancient dance passed down for centuries began.

A sharp gleam flickered in Kashu's eyes as he thought to himself.

Within this ancient inheritance, there may be a secret capable of overturning everything I know.