15 km north of the Demon Slayer Corps headquarters.
A campsite. Or rather what had once been a campsite.
Firelight stained half the sky a dark, smoldering orange. Seven or eight makeshift wooden sheds had mostly collapsed. From the broken crossbeams hung half-burned banners, still fluttering, banners painted with twisted images of buddhas and esoteric symbols, the ink now blurred and licked away by the flames.
Bodies lay scattered across the ground. Not many. Five in total. Two men. Three women. The youngest among them, a girl who looked no older than fifteen or sixteen, lay on her back beside the crude altar at the center of the camp. Two neat rows of teeth marks punctured her throat. Her blood had long since drained away. The expression on her face was frozen at the very pinnacle of terror. Her hand still clutched a string of wooden prayer beads.
The beads were crudely made, nothing like the ritual implements of a proper temple. They looked more like something fashioned by some heretical, fringe esoteric sect. Carved upon them were not orthodox Sanskrit characters, but a bizarre fusion of Buddhist and Shintō motifs.
Beside her lay a fallen banner, bearing four characters: Tachikawa Shinkyō. The Tachikawa Sect. One of the most infamous heretical cults within esoteric Buddhism.
In the name of yin-yang union and attaining buddhahood in this very body, they practiced debauched rituals and dark sorcery, preying upon the ignorant common folk across the countryside.
The cruel irony was that, in an age of endless war, such heretical cults often became the last lifeline for common people pushed to the brink of despair. This camp had been a Tachikawa stronghold. But this place was not like other Tachikawa camps.
Because a demon had broken in. A demon, twisted from humanity.
It crouched in the wreckage of the largest shed behind the altar, blood-froth still dripping from the corner of its mouth. Its ashen-gray skin gleamed with a sickly luster beneath the firelight. Its clouded, jaundiced eyes stared at the torchlight surging down from the mountain path.
It let out a rasping cackle. Filled to the brim with nothing but contempt. This was the attitude most demons held toward the Demon Slayer Corps. The casualty rate of that demon-slaying organization was always terrifyingly high.
More often than not, even when multiple swordsmen coordinated an ambush, they would still be slaughtered in return by a single demon. Demons did not fear ordinary injury. Even a Nichirin Blade, if it could not sever the neck in a single instant, was insufficient to truly harm them.
And no matter how elite the swordsman, they were still human. Humans got injured. And once injured, they grew weaker. So terribly fragile.
"The Demon Slayer Corps is here again!" it crowed. "Last time you came with five. Three died. Two fled. How many this ti—"
Its words never finished. A blade-light of blazing crimson cut across its field of vision. It carried the temperature of combustion. That dark-cyan Nichirin Blade, in this single strike, blazed with a color it had never before displayed.
Along its cutting edge, a thin layer of orange-red light shimmered. Not yōkai-fire. Not reiryoku. Pure heat, squeezed forth in the instant of the slash by human breath and human will.
Blaze, The Breath of Flame. The demon's head flew from its shoulders. It didn't even have time to register what had happened. The severed cross-section of its neck was scorched black. Carbonization spread inward from the wound.
The sunlight properties carried by the Nichirin Blade had been catalyzed by that layer of orange-red heat, burning at a speed countless times faster than ever before. The head began to disintegrate before it even hit the ground. Shattering into ash. Scattering into the night wind.
Rengoku Jinjūrō sheathed his blade. His chest heaved violently. Veins bulged on his forehead. Sweat dripped from his chin. His breathing was ragged, the brief, hollow exhaustion that followed the release of a Breathing Technique.
The Breath of Flame. He had done it. Yet it was different from the Breath of the Sun. Different from Yoriichi's breath. It was something he had wrung out of his own marrow through desperate, all-out effort over the span of days.
From his hands, which had gripped torches more times than he could count. From over a decade of hunting demons through deep mountain forests in the dead of night. It was his own light. "I did it…" Jinjūrō murmured. The hand gripping his blade still trembled faintly.
Behind him stood two young Demon Slayer swordsmen. The very same man and woman who had been subdued by Yoriichi alongside him. But in addition to them, there was one more figure who should never have been on the front lines.
Chō, She wore the black uniform of the Demon Slayer Corps, a white outer robe patterned with violet draped over it. Her butterfly-patterned mask was pushed up above her forehead, revealing a face flushed from the long, forced march.
A Nichirin Blade hung at her waist. The very blade Shinji had forged in the Swordsmith Village, the one he had gifted her. She should not have been here.
Kakushi operatives belonged to logistics, not the front lines. That was an iron rule of the Corps. But in those few days Shinji had remained at headquarters, this girl had, without question, become a test subject for the dissemination of the Breathing Techniques alongside Rengoku Jinjūrō.
Tsugikuni Yoriichi had instructed Rengoku Jinjūrō. Shinji had instructed her. The plan was to use these two as the nuclei to spread the Breathing Techniques throughout the entire Demon Slayer Corps.
In those few days, though she had not achieved a personal breakthrough like Rengoku Jinjūrō, she had learned to use the Breathing Techniques to amplify her body, accomplishing feats that had once been beyond her. Her talent for the sword was not poor. It was her stamina that had always held her back.
That was why she had failed the selection. The Breathing Techniques filled that gap perfectly. Thus, she had received special permission from Ubuyashiki to step onto the front lines, breaking precedent as a Kakushi.
The burly man stared at Rengoku Jinjūrō's blade, his eyes wide, his mouth agape, unable to close it. The female swordswoman's hand rested on her Nichirin Blade, but she had forgotten to let go. Her attention was wholly consumed by the scorched-black cut left by that single strike.
Chō's expression, however, was calm. She had seen a blade far more terrifying than this.
"Captain… that slash just now…" the burly man began.
"Move." Jinjūrō did not acknowledge the praise. He turned and looked toward the corpses in the wreckage. His footsteps were heavier now. Though he had mastered the Breathing Technique, faced with such a scene, there was not a trace of exhilaration in his heart. Only a deeper, more urgent weight.
He walked over and crouched beside the dead girl. Her hand still clutched that crude string of prayer beads. Jinjūrō gently pried her fingers open, pulled the beads free, and glanced at the twisted symbols carved upon them. He sighed and set them aside. Then he closed her eyes.
These people had been lured by the Tachikawa heresy, gathering in this desolate mountain camp to practice their so-called "true dharma." If it had only been that, they wouldn't have died. If that demon hadn't broken in… In an age where human lives were worth less than weeds, survival was everything.
"Remember her," he said without turning back. His voice was as heavy as a stone sinking into deep water. "Every single person who dies because of demons, we must remember them. And then... we avenge them. With everything we have. We cut out the source."
Upon the mountain slope. Moonlight and firelight bled into one another. Tsugikuni Yoriichi stood at the highest point of the mountain path, gazing down at the wreckage of that heretical camp below. His deep crimson eyes reflected the ruins and the corpses.
They reflected Rengoku Jinjūrō's back, crouched beside the dead girl. They reflected those who had been seduced by the cult, only to meet an innocent slaughter.
In an age of endless war, this was the norm. Soldiers rampaging. Human lives trampled like weeds. But the existence of demons still left Yoriichi with a profound, uncomprehending confusion.
"…Why?" he spoke, his voice very soft. "They were human once. I can see it, the human shape within them. Twisted, yes. But it is undeniably human. If they were human… why do they eat humans?"
This was something Yoriichi had wanted to ask long before now. If it were yōkai devouring humans, Yoriichi would not ask. If it were simply killing, killing driven by one's own desires, he would likewise not be puzzled. This was an age of chaos. Such things were only to be expected.
Yoriichi might step in to stop them, but he would not be so naive as to believe they did not exist in this world. But what he now saw, humans, twisted in will, driven to devour others, not out of desire but out of compulsion, this he could not fathom. The purpose of the being who lay behind it all.
As Yoriichi's words fell, a gray-robed figure leaned calmly against a tree trunk beside him. A bamboo hat hung against his back. White, flowing hair fell on either side of his face. Crimson demon eyes glowed faintly beneath the moonlight.
Shinji did not answer right away. He, too, was gazing down at the scene below. But what he saw was more than what Yoriichi saw. With his naked eyes, he watched the scorching heat-waves of Rengoku Jinjūrō's Breath of Flame billowing into true, blazing fire. Not an illusion. Not a mirage. Real, tangible flame.
This was different from the original Demon Slayer, yet it aligned perfectly with the evolution of this merged world. And beneath the unfurled soul-perception of his Soul-Chasing BowArm Transformation, he saw something else.
In the final instant before that demon was reduced to ash by Jinjūrō's blade, the last fragments of its residual soul flickered past. And he heard it, an exhalation. So brief. Not the terror of impending death. Not rage. Not even resentment. Only relief. Like a sigh of release. At the moment of its death, all that demon had felt was... Finally. It's over.
"Because they have no choice," Shinji spoke. "When Kibutsuji Muzan's blood invades a human body, it alters the host's very will. To them, eating humans isn't a matter of growing stronger or weaker. It's hunger. An endless, unending hunger."
"If they don't eat humans, they'll starve to death. If they do eat humans, they only grow hungrier. The stronger they become, the deeper the hunger. This isn't something willpower can fight. It's no different from a human trying to will themselves to stop breathing."
Yoriichi said nothing. But his brow furrowed even tighter. Shinji straightened from the tree trunk. His crimson demon eyes gazed down the mountain slope at Jinjūrō's silhouette, still closing the eyes of the dead.
"Do you know where the swordsmen of the Demon Slayer Corps come from?" Yoriichi turned his head to look at him.
Shinji's voice was as flat as if he were recounting the most ordinary thing in the world. "They're the ones who were left behind. Every single member of the Corps, without exception, they are people whose families were slaughtered by demons. The ones who survived. When Jinjūrō was twelve years old, a demon broke in and tore out his mother's throat. She died right in front of him. If the Corps hadn't arrived in time, he would have died too. They were just one step too late."
Yoriichi remained silent.
"And that female swordswoman who came with him, " Shinji continued. "She was originally the daughter of a merchant household in the Kansai region. The winter she was fourteen, a demon smashed through the door and devoured six of the seven members of her family. She survived by hiding in the rice barrel, masking her scent with rotting grain until the Corps arrived to pull her out. And that burly man, he's the son of a fisherman from the Tōkaidō. A demon attacked their boat. Twelve people on board. Two survived. The other went mad that very night. The next day, he threw himself into the sea."
The wind swept up from the valley, carrying the scent of charred wood and blood. All of this, Shinji had learned over the past few days.
"Every member of the Demon Slayer Corps is the same. They escaped death by a hair, were saved by the Corps, and then joined it. After two years of training, they were given a choice, join the Kakushi, or step onto the front lines. Knowing full well the horror of what demons are… they still chose to face them. They face the demons that rampage across this world. And they face the demons within their own hearts. The Demon Slayer Corps has no lofty ideals." Shinji's demon eyes lowered. "They just want revenge. And they don't want the same thing to happen to anyone else. That's all."
Yoriichi stood on the mountain path. His deep crimson eyes betrayed no emotion beneath the moonlight. But Shinji noticed, the hand gripping the Nichirin Blade at his waist had tightened.
That hand had never gripped so tightly before. From the moment they had met until now, that hand had always rested on the hilt light and easy, because Tsugikuni Yoriichi's strength had never required force. But now, he was gripping it.
Because…
"I can see it," Yoriichi finally spoke, his voice very low. "Those who have been turned into demons… traces of their humanity still remain within them. But even if it is not of their own will, they do, truly, kill people. And their victims had no choice, either." He paused. "So they must be cut down. Not out of hatred. But because… there is no other way."
The mountain wind blew past, stirring the crimson hair at his forehead. The flame-like birthmark seemed to glow faintly beneath the moonlight.
"Sir Shinji."
"Mn."
"The Breathing Techniques… we've confirmed they are viable. So I will teach them. To more people." He spoke it calmly. But Shinji heard it, the resolve.
Tsugikuni Yoriichi had finally found his reason to draw his blade. Not, as in the original course of fate, ignited by the death of his family into a flame of vengeance. Not summoned by the mission of the Demon Slayer Corps.
Simply because he had seen, people were suffering. And he happened to possess the strength to end that suffering. And he would not allow anyone to so grotesquely twist the meaning of life itself.
It was that simple. Nothing more.