Half a day later, Rengoku Jinjūrō was crouched on the ground, hands braced against his knees, gasping for air. His face was flushed crimson. Sweat streamed down his forehead and dripped onto the stone pavement with audible patters. His chest felt as though someone had stuffed a ball of fire inside, scorching, suffocating.
He had failed again. The fundamentals of the Breath of the Sun that Tsugikuni Yoriichi had taught him, he could barely manage them. But only for about twenty breaths. After twenty, his lungs felt ready to burst, and he was forced to stop.
"No… still not right…" He panted, his brow furrowed. His rough, calloused hand thumped against his own chest. The core of the Breath of the Sun was to fuse the heat of the sun into the breathing cycle.
But that fusion required the body to possess an immensely high tolerance. Body temperature spiked. Blood circulation accelerated. The heart's workload skyrocketed.
An ordinary human body simply could not bear it. Yoriichi could do it because he was born that way. The Transparent World granted him absolute control over his own physical state, the diameter of every blood vessel, the tension of every muscle, he could govern it all perfectly.
But Rengoku Jinjūrō had no such gift. He could only rely on the body he had trained through a lifetime of effort, strong, by ordinary standards. But raw, brute training was clearly not enough.
"Jinjūrō." Yoriichi crouched beside him. His deep crimson eyes watched him with perfect calm. "The Breath of the Sun… may not be suited to you." He spoke the words plainly. But Yoriichi had always been this way. He could not speak falsehoods. Rengoku Jinjūrō froze. "Not suited to me?"
"Every person's body is different." Yoriichi stood, resting the Nichirin Blade across his shoulder. "I believe the Breath of the Sun is the sun itself. There is only one sun. But when its light falls upon different places, it takes on different colors. You do not need to learn the sun. You need to find your own light."
Rengoku Jinjūrō fell silent. His own light. He looked down at his hands. Hands covered in calluses. Covered in old scars. And then, suddenly, he thought of it. Fire. His hands had gripped torches more times than he could count. When tracking demons through the deep mountain forests at night, the torch was the only source of light. Flame. Burning. And, Blaze.
"Blaze…" he murmured the word under his breath. His family name, Rengoku. Was that not itself another manifestation of flame? It was his family's legacy. Yoriichi glanced at him and smiled. He nodded in encouragement. "Try."
Across the courtyard, Shinji was no longer watching them. He had closed his eyes, seated cross-legged upon the stone platform. The Nichirin Blade still lay across his knees.
In just this short span of time, its Affection had climbed from 16 to 18. Not fast, but not terribly slow, either. Even though the power of sunlight within the Nichirin Blade refused to accept his yōki, like two magnets of the same pole, the closer they drew, the greater the repulsion.
But the yōkai-fire within his body, during the process of making contact with the Nichirin Blade, would occasionally produce a fleeting resonance. A resonance so brief it existed only for an instant.
In that instant of resonance, the power of sunlight would begin to accept him. Briefly, it would treat him as kin. He was using these scattered, fragmentary windows of resonance to seep in, bit by bit. Like water wearing through stone.
But his attention, in this moment, was not fully on the Nichirin Blade. He was simultaneously pondering another matter. The complete framework of the Breath of the Sun he had memorized from Tsugikuni Yoriichi in a single glance.
Memorizing and being able to use, were two entirely separate things. Because his lungs were dead. As a demon warrior, his body had already died at the moment of transmigration. Later, he had been resurrected by the System. He was driven by yōki. Through transformation after transformation, he was gradually coming back to life.
But that "life" moved from the outside in. At least, for now, the vast majority of his body was still dead. Only his blood had transformed. Only his bones could grow. Beyond that, the living heart and kidneys, they were only projections of the Shura Form. And his lungs, the organs responsible for breathing, were still dead.
He did not need to breathe. Every breath he took was an illusion simulated by yōki. Air entered his lungs, then was expelled. The process of oxygen exchange simply did not exist. So he unquestionably could not learn the Breath of the Sun.
It was a technique built upon the pulmonary functions of a living person. It required genuine gas exchange. It required the fluctuation of blood oxygen concentration to drive the amplification of bodily functions.
But, what if he did not walk the path of the Breath of the Sun? The core of the Breath of the Sun was the sun. The sun belonged to Yang. Belonged to Fire. Belonged to Life. That was Yoriichi's path. It was also the path of the living. But he was a yōkai. He was a demon. He had not yet truly come alive.
The Breath of the Sun illuminated all creation, bestowing strength upon the living. It was, without question, the breath of the heavens. He was not in the heavens. He was beneath the earth. In the cleft between Yomi and the world of men. At the boundary between death and life.
For an existence that had already died once to mimic the breath of the sun, was, from the start, like climbing a tree in search of fish.
But… what if he did not borrow light from the heavens above? What if he drew breath from the earth beneath his feet, from the imagined Yomi, the underworld? Let Yomi replace the sun. Let yōki replace air. Let the pulse of the dead replace the breath of the living.
The Breath of the Sun was a living person breathing the sun in the heavens. Then he, would breathe the Yomi beneath his feet.
The framework of the thought crystallized. Shinji opened his eyes. The violet veins and orange luminescence within his crimson demon pupils flared simultaneously.
He raised his hand, palm facing upward. And then, he drew a breath. Not with his lungs. With his yōki. The yōki across the surface of his body suddenly contracted, drawing the diffuse impure energies of the world into his body.
The impure energy flowed through his mouth and nose into those dead lungs. The lungs did not move. But the yōki did. The impure energy swirled, condensed, coiled within the residual structures of his lungs, and then spiraled, forming a tiny vortex.
That vortex was spinning. Slow and heavy, carrying the cold, dense thickness of the impure energy between heaven and earth. Unlike the blazing, expanding heat of the sun, it sank downward, as though drawn by the gravitational pull at the legendary entrance to the realm of the dead.
Dragging everything into deeper, darker places. There was no scorching, radiant expansion like the Breath of the Sun. Only submersion. Sinking beneath the earth. Sinking into the kingdom of the dead. Sinking into that eternal darkness to which all things must one day return. As though a gate to Yomi had opened within his body.
The impure energy drawn in spiraled once within his lungs, then was pushed back out by his yōki. But in the instant it was expelled, that impure energy was no longer the same as before. It had been filtered. Refined. Purified. It had become denser, purer yōki—yōki better suited for a demon to absorb. Yōki to drive a demon's body.
If the Breath of the Sun was the blessing the sun bestowed upon the living, lluminating all things, causing them to grow, then Shinji's breath was more akin to the blessing Yomi bestowed upon the dead. Settling all things. Returning them to their roots. His lungs did not breathe air. Yet they could filter and purify the impure energies of the world and expel them anew.
Just as the road to Yomi was a path of death, yet also the starting point of all rebirth. One in the heavens. One beneath the earth. One granted life. One commanded death. The end of the Breath of the Sun was light. The end of the Breath of the Demon was stillness.
Yoriichi had been born with the Transparent World, allowing him to perfectly command the breath of the sun. Because he was a living man. A chosen son graced by the sunlight.
But Shinji had died once. His lungs were dead. The greater part of his body was dead. So the breath of Yomi, that was the breath that truly belonged to him. The living breathed the light of the sun. The dead demon breathed the depths of Yomi. Each walked their own path. Each held their own pinnacle.
This was… the Breath of the Demon. Oni no Ko. The Demon's Breath. It was not the breathing of air. It was the breathing of Yomi itself. Dead lungs as the furnace. Impure energy as the fuel. Yōki as the converter. Inhale. Refine. Circulate.
And in the instant that first Demon Breath was completed, deep within his thoracic cavity, within those long-silent, dead lungs, something flickered. Exceedingly brief. A dark, shadowed light, suspended between black and violet, abruptly condensed where his lungs lay.
As though the entrance to Yomi had split open a fissure between two withered leaves of lung. Then, it extinguished. A single flicker, and it was gone. Something was still missing.
[Nichirin Blade (Affection: 32. First Talent 'Demon Slayer' unlocked, specialized effectiveness against demons). Its founding purpose is 'to slay demons.']
It lacked the full-Affection talent. Shinji understood. The Nichirin Blade was only a demi-demon artifact, not a fully realized demon artifact. Relying solely on the talent granted by maxing its Affection would not be enough for Shinji to complete yet another Shura Form projection. But combined with his comprehension of the Demon's Breath, it would be enough.
The Nichirin Blade and the Demon's Breath complemented one another perfectly. Its Affection had leaped from 18 to 32. The resonance was ferociously intense. But it was still not enough. Simple conversation and feeding alone seemed insufficient to drive its Affection to max any faster.
It still needed, to slay demons. The very reason the Nichirin Blade had been born was to sever the immortality of demons. If he did not fulfill the purpose for which this blade existed, the blade would never truly accept him. That could not be resolved by infusing yōki. It could not be fooled by sweet words. What it demanded, was action.
That flicker of Yomi's light just now had, beyond any doubt, already pointed the way. The form of the Shura Lungs existed. It merely required the right conditions to be awakened.
And at the same time, the thin layer of dark, cold mist that had overflowed in the instant the Demon's Breath took form, though fleeting, had already been enough to bring about another change.
Shinji looked down at the Nichirin Blade across his knees. The color of the blade had shifted. From its original pale orange luster, it had become an impossibly deep, shadowed hue suspended between black and violet. As if it were the very color of Yomi itself.
This was the origin of its name as the Color-Changing Blade. Black shot through with violet. Violet sunken into black. A color the sun could never reach. A color that could only be stained by an existence that had died once before.
"From now on… I will call you Yomi-giri." The Nichirin Blade, Yomi-giri. Also known as Fushizan, the Undying Slash. A perfect parallel to Onikiri and Raikiri.
On the veranda, Rengoku Jinjūrō was still attempting to fuse the concept of flame into his breathing. Though the path had begun to take shape in his mind, he had clearly not yet found the gate. The young man's forehead bulged with veins. His face was as red as a boiled shrimp.
Then, from the corner of his eye, he caught the fleeting, shadowy dark mist that had flickered across the stone platform on the other side of the courtyard, and the abrupt shift in the Nichirin Blade's color.
And the faintly opened eyes of that yōkai, within those crimson demon pupils, a dark and bottomless light had appeared, as deep and profound as the abyss of Yomi itself.
Rengoku Jinjūrō's movements stopped. His mouth opened, then closed. He turned his head to look at Yoriichi. Yoriichi was also looking in that direction. Within those deep crimson eyes, genuine surprise flickered for the very first time.
"He…" Rengoku Jinjūrō's voice was tinged with disbelief. "Sir Nakai… learned it?"
Yoriichi did not answer. But his eyes, the eyes of the Transparent World, told him that something within that yōkai's body was indeed undergoing a transformation.
Though the change seemed incomplete, as though it had only just begun, it was, in its own way, deeper and more complex than even his own Breath of the Sun. That was no mere Breathing Technique.
It was a metamorphosis that used breath as a bridge to reshape one's own internal circulation. "Sir Shinji… is a truly remarkable yōkai. Unlike any other," Yoriichi murmured. He offered no further appraisal.
On the veranda, Rengoku Jinjūrō crouched on the ground, looking from Yoriichi to Shinji, and finally down at his own hands, hands that had yet to find the gate.
After a long, stifling pause, he forced out a single sentence. "…What the hell am I even doing." That man had only been introduced to the Breathing Techniques half a day ago. And now he had already created his own.
While he—he was still coughing. And that was a yōkai, no less. A yōkai… sharper than any human. Jinjūrō expelled a mouthful of impure breath, clenched his fists, and forced himself back to his feet. He was fiercely unwilling to accept this.
After all, sheer dogged unwillingness was the fuel that the Rengoku family burned best. "AGAIN!" he roared toward Yoriichi. Then he drew a deep breath, and coughed again. Yoriichi could only sigh. Shinji couldn't help but laugh.
At the same time, elsewhere within the rear courtyard of the Ubuyashiki estate, Chō sat at the edge of the veranda. Before her lay a set of tools for mixing medicines. Yet the pestle in her hand had stopped. Her gaze had lifted, as though reaching across the courtyard to fall upon somewhere else entirely.
It lingered for a very long time. So long that the figure who walked up beside her finally tapped her lightly on the top of the head. "What are you staring at?"
The braided girl, one of the Seven Hashira, stood beside the veranda, a faint smile on her lips. "Sister, you're back?" The braided Hashira was, without a doubt, Chō's elder sister. Two sisters born of the same blood. The elder sister, prodigiously gifted, had already risen to the rank of Hashira.
The younger sister, with no such talent, was only a Kakushi. The gap between them could not be called small. Yet their bond seemed as strong as ever.
The braided girl's smile was gentle. "I've been watching you for nearly a quarter of an hour now."
"I was thinking about something."
"About what?"
"About…" Chō's pestle turned idly. In the end, she chose an answer that sounded reasonably logical. "About what I saw. The iron flowing down from the mountain on its own."
The braided girl was silent for a moment. She had just returned from patrol today and had already heard about that from the others. Seventy-two Nichirin Blades. Completed in a single day. All the ore had entered the furnace of its own accord.
The smiths had merely stood by and watched the entire time. Her reaction at the time had, naturally, been impossible. As a Hashira, she had visited the Swordsmith Village many times. She knew well the grueling difficulty of forging a Nichirin Blade. But after hearing the full account, and seeing the seventy masterless Nichirin Blades filling the storehouse, all that remained was silence.
Still, "What's there to think about?" The braided girl tapped her sister's head with a finger. "That gentleman… is a guest whom even the Master holds in the highest respect." She seemed indifferent. But Chō knew her sister was lying. An additional Nichirin Blade, for a swordsman of the Demon Slayer Corps, meant one more chance to slay a demon. It was profoundly important. But she didn't expose her.
The two sisters sat at the edge of the veranda. For a while, neither spoke. The wind in the courtyard carried the fragrance of wisteria, swirling it around them, laced with a strange, subtle sweetness.
"Sister," Chō said after a long pause, her voice lower than before. "Do you truly believe… that Sir Nakai Shinji can help us kill the Progenitor of Demons?"
"Perhaps he can. Perhaps he cannot. Who can truly know?" The braided girl turned her gaze slightly, answering without hesitation. "But I believe he may well be the strangest, and most honored, guest the Demon Slayer Corps has ever had."
"…Mn." Chō looked in that direction and nodded deeply. Though it had only been two days, that yōkai, that gentleman, had left an indelible impression on the girl.
The braided girl departed soon after. Chō tucked the matter away in her heart and resumed turning her pestle. The wind in the courtyard swayed the clusters of wisteria.
Two or three petals drifted down onto the stone floor beside the veranda. And then, they stopped. They did not roll further.
As though something had gently pressed them still. And in that same moment, the wind carried the sound of laughter from the neighboring courtyard.
Chō stared at those petals for a long moment. She listened to that laughter. And it was as though she once again saw those crimson demon eyes. That figure, cold and severe on the surface, yet so strangely gentle toward all things.
When she came back to herself, she realized the herbs in her hand had been ground into powder. She stared at that heap of powder, touched the Nichirin Blade at her waist, and let out another silent sigh.
She made a firm resolution: the next time she went to watch a spectacle, she would keep a distance of at least two courtyards. Compounding medicine, one must never let the mind wander.
She could not betray this blade. She must work even harder, Chō… But come to think of it "Could I… learn the Breathing Techniques too?"
Hearing the conversation drift over from the next courtyard, the thought bloomed in Chō's mind. Before, she would never have entertained such a notion. But now, the Nichirin Blade at her waist had ignited that longing. She wanted…
"You can try."
The voice came without warning. Chō's mind wandered again. She snapped back to the present. And this time, she truly found herself staring up into a pair of demonic eyes that had materialized above her, appearing and vanishing like a phantom.
A startled cry escaped her lips.