Thud.
Oboro paid no attention to Muzan's anguished roar of desperation, his expression remaining as impassive as carved stone. The Demon King's final scream echoed through the Infinity Castle before being swallowed by an oppressive silence that seemed to drain all warmth from the air.
After a heartbeat that stretched into eternity, the light in Muzan's scarlet eyes flickered and died like a candle extinguished by winter wind.
His body crumpled to the platform with the finality of absolute defeat.
Oboro activated his system's unique functions, watching as Muzan's blood and Blood Demon Arts transformed into glowing data cards that materialized in his hand. The process was swift and clinical—centuries of accumulated power reduced to portable essence in mere moments. Once the extraction was complete, he exerted his soul pressure with surgical precision, crushing what remained of the Demon King's consciousness like stepping on brittle glass.
The obliteration was total and irreversible.
In Oboro's enhanced perception, the will of the Demon Slayer world—that metaphorical "little tree" he'd been cultivating for decades—trembled with unmistakable displeasure. Its spiritual emanations carried the petulant quality of a child whose favorite toy had been broken.
"Everything he possessed was my gift, given to him twice over," Oboro responded to the world's unspoken protest, his mental voice carrying the patience of a teacher addressing a slow student. "His greatest value lay in catalyzing the growth of other seeds through competition and conflict, not in growing alone while absorbing all available nutrients. Do you understand?"
The little tree's preference had been obvious—it wanted Muzan to become the ultimate antagonist, a final boss whose overwhelming power would drive heroes to transcendent heights. But such an approach would have stifled the very diversity that made power systems truly robust.
From Oboro's perspective, if Muzan had been allowed to eliminate his rivals and consolidate demonic power under his sole authority, the long-term consequences would have been catastrophic. Even with enhanced abilities, the Demon King would eventually face the full might of the evolved Demon Slayer Corps. Victory wasn't guaranteed, and defeat would mean the complete extinction of demonic power from this world.
At best, Muzan's survival would have prolonged the conflict for a few more decades without fundamentally changing its nature.
Where was the intensification in that? Where was the evolutionary pressure that drove real growth?
If Muzan had truly won tonight through his own merit—if his strength and will had developed to the point where victory was genuinely earned—then Oboro would have gladly honored their agreement and allowed him to shape this world's future. But that hadn't been the case.
Throughout their recent battle, Oboro had observed Muzan's soul with the clarity of absolute perception. Even while consuming his spiritual energy to dangerous extremes, the Demon King had entertained thoughts of retreat more than once. Only his terror of Oboro's judgment had suppressed those cowardly impulses and forced him to continue fighting.
Such a mentality revealed fundamental character flaws that no amount of power could overcome. Even if Muzan possessed the raw strength to defeat either Doma or Gyutaro individually, his psychological weaknesses would have reduced his actual chances of victory.
That was the crucial difference between potential and reality—the gap that separated true leadership from mere dominance.
"His strength grew considerably," Oboro mused with analytical detachment, "but his essential nature remained unchanged."
In this critical aspect, Muzan had proven inferior to both Doma and Kokushibo. Those two demons had demonstrated genuine evolution of character alongside their enhanced abilities.
Two platinum cards materialized in his palm—one containing Muzan's bloodline essence, the other his signature techniques. Both represented the culmination of over a millennium of demonic development, compressed into portable forms that could be utilized in entirely different realities.
With a casual flick of his fingers, the cards vanished into his inventory.
Immediately, Oboro's attention shifted to the distant sounds of ongoing combat. Sharp slashes and crystalline explosions echoed through the dimensional space as the battle between Doma and Gyutaro reached its crescendo. Debris from their devastation—fragments of destroyed buildings and shattered platforms—tumbled into the endless abyss below the Infinity Castle.
The conflict had entered its most intense phase, but Oboro felt no compulsion to observe its conclusion. Regardless of which demon emerged victorious, they would be transformed by the experience, elevated to new heights of power and understanding. The victor would become the natural leader of this world's demonic faction, setting the tone for decades of future conflict.
More importantly, the spark of inherited will continued to burn among the scattered survivors of his original followers. Though most first-generation inheritors had perished tonight, their chosen successors remained active throughout the land. As long as they maintained their conviction that this world was fundamentally broken and corrupt, as long as they opposed the established government and its defenders, the flame of rebellion would never be extinguished.
Both Gyutaro and Doma possessed the character necessary to guide that flame. Gyutaro dreamed of transforming the world into a realm of endless slaughter where only the strong survived. Doma's worship of Oboro had evolved into a sophisticated understanding of manipulation and control—if he survived, he would likely attempt to recreate Oboro's methods, treating entire populations as pieces in an elaborate game.
In the ice demon's twisted worldview, human beings were inherently stupid and ridiculous, their lives holding no intrinsic value beyond their utility as entertainment or resources. Such contempt for conventional morality would naturally lead to conflicts that pushed the boundaries of what this world's inhabitants could achieve.
Either path would serve Oboro's ultimate purpose.
Neither demon possessed Muzan's raw power, but both had demonstrated superior force of will and clearer vision for the future. When they eventually died—and death would come for them eventually—new champions would rise from the ranks they'd trained and inspired. The cycle would continue, each generation building upon the achievements of those who came before.
"What I've done represents the optimal outcome," Oboro communicated to the world's governing will, his mental voice carrying the weight of absolute certainty. "Don't interfere anymore. If you continue manipulating their fates according to some predetermined script, this world's power will stagnate and may eventually disappear entirely. You'll degenerate along with it."
He paused, allowing the implications to sink in before delivering his final warning.
"If the consequences become severe enough, you won't just be relegated to lower-world status—you might become an ordinary reality entirely, stripped of all supernatural potential."
The world's will shivered at the prospect, its spiritual emanations reflecting genuine fear for the first time since their partnership began.
"Most importantly," Oboro continued with inexorable logic, "don't let the Demon Slayer Corps achieve total victory."
If the Corps eliminated all demonic threats permanently, peace would inevitably follow. Just as in the original timeline, breathing techniques, swordsmen, and demons would gradually fade into legend as humanity moved on to other concerns. While Oboro had planted seeds of power throughout the general population, there was no guarantee those gifts would be preserved without external pressure to maintain them.
The complexity of human nature represented both the greatest asset and the most dangerous weakness in any power system. Where people gathered, conflict was inevitable—but intelligent societies also developed methods for containing and channeling that conflict into non-destructive forms.
If future governments managed to implement laws and regulations that successfully restricted supernatural abilities, they would essentially achieve peace through systematic suppression. As conflicts decreased, the rate of power development would slow correspondingly.
Unrestricted power and lawless chaos had always been the most fertile soil for breeding strength. Comfort and security were the enemies of transcendence.
After completing his communication with the little tree, Oboro severed their mental connection and withdrew from the Infinity Castle. His work in this dimension was finished.
Time flowed like a river carrying away the debris of old conflicts.
Decades passed in what felt like the blink of an eye, and the world had transformed beyond recognition. The plot that should have begun had opened along entirely new trajectories.
On Mount Kumotori, Tanjuro Kamado's son—the boy who should have been the protagonist of this world's greatest story—had grown into a capable young man who helped his father sell charcoal in the nearby towns. Their family had never been attacked by demons, and Tanjiro had passed well beyond the age when he should have joined the Demon Slayer Corps.
The Corps itself had evolved into something unrecognizable from its original form. In addition to the Hashira from the traditional timeline, many new faces had risen to prominence. Tomioka Giyu, Rengoku Rengoku, Kanroji Mitsuri, and Uzui Tengen all served with distinction, but the organization's structure had expanded dramatically.
Kocho Shinobu remained a dedicated follower of the Flower Hashira Kanae, who had never died in this altered timeline. The preservation of experienced veterans, combined with the enhanced training methods Oboro had introduced decades earlier, had produced a generation of demon slayers whose skills far exceeded anything from the original era.
Most remarkably, the current generation boasted fifteen active Hashira—a number that would have been impossible under the constant attrition of the past.
Ubuyashiki Kagaya served as their leader, though his family's ancient curse had been broken with Muzan's death. This liberation had allowed him to perceive the true scope of the changes reshaping their world.
For while Muzan was gone, the threat of demons had not diminished. If anything, the situation had grown more dire than during the Demon King's reign.
The creature now standing at the apex of demonic power represented a different kind of nightmare entirely.
Ubuyashiki Kagaya closed his eyes, reflecting on the mystery that had haunted him for decades. Muzan's death remained unexplained, though he strongly suspected it was connected to Gyutaro somehow. The truth, when he'd finally pieced it together from scattered reports and historical records, painted a picture of tragedy and manipulation that chilled him to the bone.
Gyutaro had gone insane after Daki's death. For years, the siblings had been inseparable, their symbiotic bond documented in numerous intelligence files. But Daki had been killed by Doma, the former Upper Moon Two, and that loss had shattered something fundamental in Gyutaro's psyche.
The rumors suggested that Gyutaro and Daki shared some form of supernatural connection that should have made her death impossible while he lived. Doma's soul-based abilities had apparently severed that bond in ways that defied normal understanding, leaving Gyutaro to exist alone for the first time in his centuries of existence.
Since that catastrophic event—combined with Muzan's death and the complete collapse of centralized demonic authority—the world had spiraled into chaos.
Gyutaro's current strength defied description. His mental state had deteriorated to the point where normal reasoning seemed impossible, yet his destructive capabilities had grown beyond anything previously recorded. He appeared randomly throughout the land, destroying everything in his path with the single-minded determination of a natural disaster.
The Demon Slayer Corps had proven helpless against him for decades despite their enhanced capabilities. Many Hashira had fallen to his relentless assault, and even coordinated attacks involving the human government's military forces had achieved nothing but additional casualties.
This was merely the surface level of the crisis.
In Kagaya's analysis, all these dark developments could be traced back to a single individual—a name that remained largely unknown to the general public despite his profound influence on their world's destiny.
Oboro.
Not the God of Swordsmen who was now worshipped in temples throughout the land, but the actual person behind that divine facade.
Through careful study of historical records and family archives, Kagaya had developed insights that few others possessed. He understood that Gyutaro's "gift" from Oboro had been granted specifically because of the bond between the siblings. In other words, Oboro had likely foreseen the disaster that was now unfolding. Daki's death might have been not just anticipated, but deliberately orchestrated as part of some grander design.
The most troubling aspect was that Oboro had vanished decades ago, with no one knowing his current whereabouts or condition. Sometimes Kagaya wondered if the mysterious figure had died—and if so, the fact that his carefully laid "games" continued developing according to his vision made the prospect even more terrifying.
More disturbing still was Kagaya's inability to imagine what could have caused such a death. Based on everything he'd learned about Oboro's capabilities, conventional threats seemed laughably inadequate.
The wisdom accumulated by generations of Ubuyashiki leaders had allowed him to decipher the logic behind Oboro's actions. The goal hadn't been to cause suffering for its own sake, but to introduce new forms of power and create conditions where multiple factions would clash in ways that drove unprecedented innovation.
Oboro had sought to transform the world into an unstoppable arena where power could be tested, refined, and passed on to future generations.
"The promoter of history," Kagaya murmured, the label he'd assigned to the absent architect of their current situation.
Yet despite understanding the methodology, the ultimate purpose remained elusive. He'd never met Oboro personally, but the Ubuyashiki family maintained a detailed portrait based on eyewitness accounts from previous generations.
On sleepless nights, Kagaya often found himself studying that image—the face of a man whose influence had reshaped their entire reality.
"Black haori… black haori… snow mountain… corpse…"
A crow's harsh cry suddenly shattered his contemplation, the words jolting him from his reverie. When the messenger mentioned "black haori," Kagaya's pupils contracted with shocked recognition.
That garment was unique—there were only two such pieces in the entire world, and both carried profound significance.
Several days later, Ubuyashiki Kagaya personally led an expedition to the summit of Mount Asahidake, a snow-covered peak on the nation's northern frontier.
The journey had been prompted by the crow's urgent report, though Kagaya hadn't dared voice his suspicions about what they might discover. When they finally reached the mountain's peak, the scene that greeted them defied every expectation.
A man sat leaning against a massive boulder, his eyes closed as if in peaceful sleep. He was no longer breathing.
His clothing had rotted away to mere fragments, but scraps of distinctive black fabric still clung to his frame like tattered banners marking a forgotten battlefield. Despite the obvious age of his death, the corpse showed no signs of decay. His flesh retained a healthy color, his limbs appeared naturally positioned, and at first glance he might have been mistaken for someone merely resting.
Given the state of his garments, he had clearly been dead for a considerable time. Yet even accounting for the preservative effects of the mountain's climate, his body should have shown more deterioration—mummification, shrinkage, some visible sign of time's passage.
Instead, he appeared almost alive.
"It's him," Tomioka Giyu spoke before Kagaya could voice his own recognition.
The Water Hashira's voice carried the weight of inherited memory. Stories passed down through generations of his family had described this figure in perfect detail, and there could be no mistake about his identity.
"Suicide?" Kanae covered her mouth in shock, her gentle nature recoiling from the implications.
"The power of the soul," Iguro Obanai observed with cold analytical precision. "He's maintained spiritual cohesion even in death."
"The bastard ran away in the end, and even his death is annoyingly dramatic!" Uzui Tengen's outburst carried equal measures of frustration and grudging admiration. "What a flamboyant way to bow out!"
But Kagaya seemed lost in deeper contemplation, his expression heavy with understanding that the others couldn't share.
"He defeated everyone and proved himself stronger than any opponent," he said softly, "but he couldn't defeat time itself. For someone like him, the entertainment value of any world was always finite. Once boredom set in—that endless, crushing tedium—continued existence would have been more torturous than death."
His words carried the weight of philosophical certainty. "This world had become a game played entirely within his control. We never even qualified as worthy opponents."
Tomioka Giyu's hands clenched into fists, frustration radiating from every line of his body. The revelation that their greatest struggles had been nothing more than entertainment for a detached observer struck deeper than any physical wound.
At that same moment, in a town hundreds of miles away, an entirely different drama was reaching its climax.
The settlement bore the scars of recent violence—corpses scattered through streets painted with blood, buildings reduced to smoking ruins, the acrid smell of death hanging heavy in the air like a funeral shroud.
Through this devastation walked a solitary figure, his movements mechanical and purposeless. Two blood-stained sickles hung from nerveless fingers, their curved blades dripping crimson tears onto cobblestones already stained beyond redemption.
Gyutaro moved like a walking corpse, his once-keen eyes now dull and vacant. He muttered continuously under his breath—fragments of conversations with someone who was no longer there, questions directed at empty air, half-formed plans for a future that would never come.
Suddenly, a black shadow materialized in his path with the fluid grace of enhanced movement techniques.
Gyutaro raised his head with wooden mechanical precision, his grip tightening reflexively on his weapons as killing instinct overrode conscious thought. The newcomer was clearly a demon of considerable power, and in his current state, Gyutaro's response to any supernatural presence was immediate violence.
The demon's face went pale as he sensed the murderous intent radiating from the legendary figure before him. Fear lanced through his consciousness as he realized how close he'd come to triggering his own obliteration.
"Mount Kumotori!" he blurted desperately, the words tumbling out in a frantic rush. "Your sister is on Mount Kumotori! Ume… she's still alive!"
The name struck Gyutaro like a physical blow, stopping his advance as if he'd collided with an invisible wall.
"I'm not lying," the demon continued, sensing the critical moment. "Ume's soul has been reincarnated. She lives now as Nezuko Kamado."
For the first time in decades, something resembling awareness flickered in Gyutaro's hollow eyes.
In the void between dimensions, where the consciousness of the Demon Slayer world maintained its ethereal existence, the metaphorical tree swayed gently in cosmic winds.
Its branches moved with unmistakable joy, conveying emotions of satisfaction and anticipation that rippled through the fabric of reality itself.
The game was far from over.
In fact, it was about to begin anew.