Kamado Tanjiro closed his eyes... the violently swelling, bursting terror and bitter frustration left him unable to think straight, and the vast gulf in strength between him and his opponent plunged him into an abyss of despair.
But what awaited him was not death—it was that place.
A strange room, like the study of some wealthy household, with several potted flowers of different colors set about, gauze curtains swaying by the window in the breeze, the soothing scent of sandalwood filling the room, and the tick-tock, tick-tock of a pendulum clock... Seeing this scene, Tanjiro's wildly pounding heart calmed a great deal.
Beside a bookshelf along one wall sat a child in a chair, a book cradled in his hands.
"You're here again."
He set the book down and gave a faint smile.
The figure was handsome but aloof, hair combed back and short, dressed in a very avant-garde little Western formal suit. Though he looked like a child, his true age was likely beyond reckoning—Tanjiro had already spoken with him quite a few times before.
"How's it going? How's the demon hunt coming along?"
"I'm too weak."
He didn't answer head-on, but it reflected his situation all the better.
Tanjiro couldn't help picturing again the moment his blade was so easily shattered by the enemy. He ground his teeth, lowered his head in frustration, and could only endure the powerlessness that came with being weak.
"Everyone is fated to accomplish a certain purpose in this world. And you—you're a born demon slayer."
"I never wanted to be a demon slayer... I joined the Demon Slayer Corps only to turn Nezuko back into a human, and to find and kill the demon that slaughtered my family. To avenge them."
Tanjiro lifted his head, his face full of confusion and sorrow.
"But I'm too weak, sir. I can't beat that member of the Twelve Kizuki—I can't even protect Nezuko..."
"That's because you haven't used your strongest technique."
A chilling light gleamed in the bookish boy's blood-red eyes.
"Come with me."
He rose and walked over slowly, passing by Tanjiro's side, and made for the door at the back... Tanjiro quietly followed. This boy was the only person he could rely on now; he had to find a way to break the enemy's Blood Demon Art before he returned to reality.
Speaking of which, this was a secret known to Kamado Tanjiro alone.
Two years ago, his mother and younger siblings had been killed by a demon, and the sole surviving sister, Nezuko, had become a demon too. After that he'd encountered a demon slayer swordsman named Tomioka Giyu, and Tomioka-san recommended a Cultivator to him. Tanjiro trained bitterly while caring for his sister... and two years later he'd completed all his training and entered Mount Fujikasane for the Final Selection.
Pass that trial, and Tanjiro could become an official Corps member. But he'd run into a monster that had no business appearing at his level—a demon with a grudge against his own teacher, Urokodaki-sensei. Imprisoned there, it had already killed more than a dozen of Tanjiro's senior fellow disciples, all to take revenge on Urokodaki-sensei.
Tanjiro was no match for it. But just as he flagged, on the verge of defeat, his consciousness suddenly slipped into this place, where he met the mysterious boy of the dream.
That boy had no name, yet he told Tanjiro of the destiny ahead: to become the strongest demon slayer.
And there was no limit to time within the dream. Every time Tanjiro found himself in desperate straits, he could rest and recover here, or train the techniques of his Breathing.
Little by little, he'd struck down more and more demons, and his understanding of Breathing had climbed another rung.
But it still wasn't nearly enough. Tanjiro knew that to grow stronger, he had to shatter some shackle binding him.
The instant the door opened, the howling wind rang like a great tolling bell, jarring his ears until they ached—but once the door stood fully open, it all fell quiet. A pitch-black night sky, snowflakes drifting silently down... and that man dancing a kagura by the bonfire.
Tanjiro's heart gave a pang.
That was his father.
Each time the door opened, the dream boy could bring Tanjiro somewhere different.
He'd never expected that this time it would be a memory of his own from years ago. He stood off to the side, watching his father perform the rite to the fire god, with his younger self and his mother nearby.
"Why show me all this?"
Tanjiro asked, head bowed, lost and hollow.
"Your father was extraordinary." The boy admired the man's dance, some deep nostalgia buried in his gaze. "You must remember his movements well... This is the second lesson I mean to teach you—an entirely new Breathing technique."
—Tanjiro, breathe well, and let yourself become the fire god himself.
All at once, Tanjiro recalled the conversation he'd had with his father after that kagura.
"Dad, your body's so frail—how can you dance so long in the falling snow?"
"There's a knack to breathing, Tanjiro... adjust your breathing right, and you can dance forever without ever tiring."
"This kagura, and these earrings—you must pass them down, no matter what... Tanjiro."
—We made a promise.
His father's voice echoed faintly through Tanjiro's mind, and in that moment he finally understood... His father's kagura had been a kind of "Breathing" he'd meant to pass on to him all along.
This was the original Breathing technique, and the strongest of them all.
Sun Breathing.
...
...
The Lower Rank Five's name was "Rui," a fairly androgynous name, well-suited to his own image as a slender, somewhat gaunt boy.
Mount Natagumo was his private garden, where he did as he pleased. The demons here played their assigned roles, living within a "family" that Rui had built with his own hands.
His Blood Demon Art was a spider-like power of manipulating threads, the toughness of the silk beyond imagining.
A moment ago, Tanjiro—rash in his desperation to protect his sister—had charged in to cut Rui down, only for a single thread, flicked out with the barest effort, to shatter that formidable Nichirin Sword. That alone showed the difference between them.
Rui had loosed his Blood Demon Art to dye his silk red, its toughness strengthened to the utmost, dense red threads woven into a net that pinned Tanjiro in place... With a snap of his fingers he could strangle that stupid, weak fool with no self-awareness, and make his little sister part of his own family, too.
But now the situation had reversed in a heartbeat.
His proud Blood Demon Art: Cutting Thread Cage had actually been broken!
The person was still the same person, but the aura had utterly changed... Though the ruined broken blade still lay in his hand, what now wreathed Tanjiro was no longer that vast, roaring water dragon, but a serene, blade-thin flame.
That was the energy of the sun—devastating to anything at all connected with demons!
"Raging Sun!"
The boy gripped his burning broken blade and melted every thread in an instant.
His mind was perfectly calm now, and his breathing had never been steadier. He had fully absorbed both the memories unlocked in the dream and the kagura his father had meant to pass down to him!
"What... my threads, they—?"
Rui went pale with shock, but he had no time to dwell on it. He hurriedly conjured more threads to bar the boy who came on like a god of death.
"Sun Breathing, Sixth Form: Burning Bones, Summer Sun!"
In almost a single instant, Tanjiro seized on the technique best suited to the moment. Every time he was driven into that boy's dream, his strength leapt a whole tier—and now this so-called Lower Rank Five was no longer any match for him.
Tanjiro stamped hard against the ground, his body soaring into the air, the blade whirling like a firestorm around and around his frame. Before a Tanjiro like this, transparent spider silk or blood thread alike might as well have been cobwebs before a flame.
The scorching aura seared Rui's skin. Yet he still couldn't make sense of it... What on earth has this guy done? Why has he suddenly become a different person entirely—not just his strength surging, but his skill and movement flawless, without the slightest opening?
—My neck will be severed.
At this rate, my neck—my neck is going to be cut clean off!