At the same moment.
Kyōto, Honnō-ji.
This temple of the Hokke sect, nestled within the capital, was flourishing with incense and thronged with monks who chanted sutras day and night without cease. The vow-power and dharma-power of dozens, hundreds of priests formed an invisible dome that enveloped the entire temple.
Any yōki, demonic energy, or impure worldly corruption would be naturally purified and dispersed within this area. This was forbidden ground for yōkai. Absolute death for demons. And therefore, it was a hiding place no one would ever think of.
Kibutsuji Muzan's final split fragment was hidden here. Hidden deep within a crevice in the stone base of the main hall's Buddha statue. A lump of violet-black flesh the size of a fist. It emitted no aura. Produced no fluctuations.
Like a single insect egg sealed within amber. The Demon Slayer Corps could not find it. The Earth Barrier could not seep in. Yōkai, even less, would ever set foot in this place. This was Muzan's deepest contingency. To hide the final piece of himself within the most solemn, pure Buddhist sanctuary of the age.
To use medicine to conceal poison. To use purity to mask filth. As long as this lump of flesh did not actively stir, no existence in this world could discover it.
And tonight, the moment his main body was utterly annihilated by that single slash of fused Sun and Moon, within the stone crevice at the base of the Buddha statue, the violet-black lump of flesh stirred.
The movement was so faint it was almost imperceptible. So faint that even the old monk meditating before the statue noticed nothing. Regeneration began. Slow. Agonizing. Like a seed frozen for five hundred years finally cracking open its shell.
Muzan's consciousness surfaced from the chaos, shattered, fragmented, scattered like broken shards of a mirror barely pieced back together. The first thought that formed: I am alive. The second thought: I must flee. But before the third thought could even take shape, it was cut off.
"Awake, are we?"
A voice came from the darkness. Clear and gentle. Carrying a thread of pleasure that sent chills crawling up the spine. Muzan's regeneration screeched to a violent halt. Impossible.
This was Honnō-ji. Within the barrier of over a hundred monks' vow-power. No one could possibly imagine that his final splinter was hidden here. No one, not even the demons he himself had created.
"Lord Muzan… you're still thinking, 'No demon could possibly be here,' aren't you?" The voice was laced with laughter. From the darkness, within the shadows cast by the Buddha's halo, a pale female face emerged.
Elegant, understated kimono. Black hair cascading loose. Handsome, sharp features curved into a faint smile. Like an aristocratic young noble. And like a spider, poised upon its web, gazing at its prey.
"Kumo-Oni." Muzan's voice squeezed out from that lump of flesh still struggling to regenerate. Hoarse. Weak. Brimming with utter, absolute disbelief. "How… are you here? When… when did you learn of this place?" His voice shifted from hoarse to ice-cold. And even carried a thread of fear.
He had never told any demon that he had hidden a contingency within Honnō-ji. Never. It was the most tightly guarded secret he possessed. And yet, it had been discovered.
Kumo-Oni's smile deepened. "Have you forgotten, Lord Muzan?" She crouched down, her pale face drawing close to that lump of violet-black flesh. "You can read the memories of all your demons. But that ability… is, in truth, a two-way path."
Muzan's consciousness detonated. Two-way. He had never once considered this possibility. As the Progenitor of Demons, when he bestowed his blood upon a demon, he implanted within it absolute obedience.
The blood-curse ensured that no demon could defy his will. Could not betray him. Could not hide anything from him. He could read the memories of any demon. He could annihilate any demon's existence in a single instant.
This was the absolute authority of the Progenitor. But, what if there was a demon whose will was so powerful, whose obsession was so deep, whose cunning was so profound, that even as it was being read, it could peer back, in turn, into the Progenitor's own memories? Theoretically, it was an utter impossibility.
And yet, what if? What if, every time Muzan read Kumo-Oni's thoughts, Kumo-Oni had been reading his? A little at a time. Stealing, bit by bit. For an entire month. Until she had stolen, the location of Honnō-ji.
And such a level of "will," in this world, was not absolutely impossible. At the very least, Kibutsuji Muzan had glimpsed it from afar. Before he had encountered this female bandit calling herself Kumo-Oni… when he had gazed out across the vast plains of Musashi Province… it lay within the very objective of this journey. The Shikon no Tama.
"Have you realized it now?" Kumo-Oni narrowed her eyes. And within her eyes, a dark violet light, like the luster of a sacred jewel, truly flickered. It was the Jewel she had seen in her dream. The origin of her obsession with that single figure. And now, she understood even more clearly what that thing, which had pulled her back from the brink of death, truly was.
The Shikon no Tama. Or rather, a fragment of it. The residual emanation of the Dark Spirit within. A sliver of its influence. The Kumo-Oni who had been nothing more than a bandit could never, on her own, have possessed such terrifying willpower. Only this Jewel, brimming with the infinite grudges of countless yōkai, could have granted her such will.
"But in the end, it's also because your mind was not an iron fortress, was it, Lord Muzan?" Kumo-Oni sighed, her voice thick with regret. "Especially when you thought of your 'final contingency', your mental defenses were always at their weakest. Because you were at ease. And the moment you were at ease, you couldn't help but mentally revisit that place of safety. Honnō-ji. The main hall. The base of the Buddha statue. The crevice in the stone. Every detail you envisioned… I saw it all."
Muzan fell silent. That lump of violet-black flesh stopped writhing. It was as though even his regeneration had been frozen solid by fury... and by terror. But he still had one final card. The Progenitor's authority. Annihilation. As long as he still lived, he could, in an instant, obliterate any demon he had ever created.
He mobilized that authority. His will shot along the connection of blood, aimed directly at the very core of Kumo-Oni's existence. Nothing happened. The connection... had been severed. That bloodline tether stretching from Progenitor to progeny, was cut clean through, as though by invisible shears. The two ends snapped apart. Never to connect again.
"If you were hoping to destroy me, then I'm afraid it's far too late for that." Kumo-Oni rose to her feet. From the shadows behind her, another figure stepped forward.
Another woman, black hair, elegant and refined. Dressed in a subdued kimono. She appeared to be around thirty, but within her eyes, dark violet, slit-pupiled, the vitality radiating outward far surpassed the age her face displayed.
The instant he saw this woman, Kibutsuji Muzan's consciousness trembled even more violently. He knew, of course, exactly who this woman was.
Tamayo. She, too, had been selected by Kumo-Oni as a demon with the qualifications to serve among the Twelve Demon Moons. But unlike the other demons, Tamayo's Blood Demon Art was Corrosion.
To erode, decompose, and reconstruct the information within blood. To alter the scent that blood emitted. Muzan had valued her highly, though not as highly as Kumo-Oni, and had even permitted her to reside within his own estate.
After all, such an ability, in Muzan's eyes, held the potential to help him find the Blue Spider Lily. Only now, it seemed, it was precisely she who had helped Kumo-Oni sever the bloodline connection to Muzan.
"Lady Tamayo was of tremendous help." Kumo-Oni laughed, swaying with mirth. "Severing a bloodline connection... impossible alone. But with two… that's an entirely different matter."
Muzan, with tremendous effort, managed to regenerate a single eye. He stared at Tamayo. Tamayo did not evade his gaze. On her face was written a resolve so calm it bordered on cruelty.
"You two… since when have you been working together?"
"Since the third day after I was turned," Kumo-Oni answered without the slightest hesitation. "You didn't know, did you? When I found her and proposed our collaboration, she wanted to kill me at first. But I said one thing to her.... and she changed her mind." Muzan's lump of flesh quivered faintly.
"What did you say?"
"I said...." Kumo-Oni crouched down. Her pale palm covered that lump of violet-black flesh. Her fingers sank into the meat, as gentle as a lover caressing a beloved's cheek. "'Let's devour Kibutsuji Muzan together.'"
Muzan's consciousness, in that moment, went utterly, deathly cold. He finally understood. From the very beginning, from the moment he had seen that dying female bandit on the roadside and thought her the perfect vessel for demonification, he had already lost.
Not to the Demon Slayer Corps. Not to that Sun Breathing swordsman who had appeared out of nowhere, Tsugikuni Yoriichi. Not even to Nakai Shinji. But to the monster he himself had created. The monster he believed was completely under his control. The monster he had fed and raised with his own hands.
"That is why I brought the false rumor of the Blue Spider Lily to you. Why I told you that what needed investigating was not the rumor itself, but the one behind it. My 'loyalty'… you must have seen it clearly, didn't you… Lord Muzan?" Kumo-Oni's voice grew very, very soft.
"Thank you… for your blood. And thank you… for your power. Thank you… for creating me." Her mouth opened wide. It split to the roots of her ears. Two rows of jagged fangs gleamed with a cold, ghostly light in the halo of the Buddha's image. "But from this day forward, I shall be the Progenitor of Demons."
She bit down. Muzan screamed. The sound was completely contained within the stone crevice at the base of the Buddha statue by the vow-power barrier of the hundreds of monks at Honnō-ji. Not a sliver of sound escaped. Outside, the old monk turned a page of his sutra. Utterly oblivious.
The devouring was absolute. Not merely flesh, but every remnant of Muzan's consciousness, his memories, every scrap of information carried within his bloodline, was chewed, swallowed, and digested, bite by bite. The Progenitor of Demons, who had endured for five centuries, was, on this night, devoured by the very demon he himself had created.
Tamayo stood to the side. No emotion could be read on her face. But the fingers clutching her sleeves were trembling. The devouring lasted for the entire span of a single incense stick, until every last sound and movement had faded into nothingness.
Kumo-Oni rose to her feet. Her body was changing. Though her face was still that pale, handsome visage, and her form still that long-limbed, sharp-edged silhouette, her scent had transformed.
The power surging from within her body was no longer of any level a mere demon should possess. It was the power of the Progenitor. Though it was only the final sliver of blood.
The final lump of flesh. Yet its quality, its substance, was, without question, something only the Progenitor of Demons could possess. Very little. Yet very dense. Very pure. She had inherited it.
Kumo-Oni closed her eyes and felt the power roiling within her body. Then she opened them. Those eyes had changed.
A crimson so deep it was nearly gemstone-red. Within her pupils was reflected the compassionate face of the Buddha. The flickering candlelight of the main hall. And, an infinite, boundless obsession. For a single person.
Tamayo stepped back. The aura of the Progenitor of Demons radiated from Kumo-Oni's body, flooding every inch of the crevice. The oppressive weight of it far exceeded anything she had ever felt from Kibutsuji Muzan. Because Muzan's presence had been cold. Suppressive. A commanding, overbearing pressure.
But Kumo-Oni's presence was hot. Scalding. It clung to you, viscous as spider silk, winding against your skin, against your blood vessels, against the deepest recesses of your soul. Suffocating. Yet Kumo-Oni paid Tamayo no mind. She simply stood in the darkness, eyes closed, savoring the sensation of newfound power surging through her.
Then, as though she had sensed something, her crimson eyes flew wide open. Her body went rigid for an instant. Deep within her, in the deepest core of the Muzan flesh she had just devoured, at the lowest stratum of the residual remnants of Muzan's soul, there was something. Not blood. Not flesh. Not a fragment of soul.
It was… a tether. An anchor. An impossibly fine, impossibly concealed, impossibly exquisite thread of soul. And Kumo-Oni seemed to recognize exactly what it was. She began to tremble. It was the anchor of the Soul-Chasing BowArm Transformation.
When Shinji had locked onto Muzan's soul, he had already discovered this final splinter hidden within Honnō-ji. He hadn't been able to pinpoint its exact location.
He couldn't pierce through the vow-power barrier of the monks. But he didn't need to. He only needed to leave a single thread upon the entirety of Muzan's soul. No matter where that soul ultimately flowed, whether it was annihilated, or devoured, or transferred, that thread would follow. Like fishing. Only the fish was not Muzan.
Muzan was merely the bait. The fish… was whatever dared to come and devour Muzan. And so Kumo-Oni had bitten. And thus, the other end of the anchor connected, without question, to Shinji.
This—this was the true eradication Shinji sought. The plan that had crystallized in his mind the very moment he had learned of Kumo-Oni's existence.
A voice of utter comprehension, echoing with finality, detonated within Kumo-Oni's ears. "So that's how it is." On the other end of heaven and earth, upon the wilderness, Shinji had witnessed the entire sequence. At last, he understood exactly how this Kumo-Oni had come to be.
She was, indeed, the Kumo-Oni of the original story. A bandit. Yet she was also a different Kumo-Oni, born under the influence of the Dark Spirit. Her origin traced back to that night, not long after Shinji had found Kikyō.
In that brief window of time when the Dark Spirit had fled, a butterfly effect had been born. Kumo-Oni's birth. Kumo-Oni's obsession. All of it stemmed from the Dark Spirit of the Shikon no Tama.
In that moment, Kumo-Oni froze. Within her crimson eyes, it was as though a vision had surfaced. A wilderness. A waning moon. A young man with pale, flowing hair standing upon scorched-black meadow. Crimson demon eyes staring at her through the gaps of his mask.
As though looking at an insect that had just fallen into a spider's web. Only, it was not her web. It was his. Before Kumo-Oni could even react, Shinji spoke. A single sentence. Simple. Calm.
"You have eaten humans."
Across thousands of kilometers, he had truly seen it. He had seen the roiling, churning weight of grudges coiled around this "Kumo-Oni." He had seen her evil. He would not be shackled by any so-called original story. He would not assume, before ever meeting her, that this Kumo-Oni, who had not yet become Naraku, was certainly evil.
But now that he had seen it with his own eyes, what choice to make required not a shred of deliberation. Eradicate evil completely. Eliminate every potential threat in advance. It was as simple as that.
The words rose. The words fell. The voice echoed a third time. This time, Kumo-Oni reacted. And felt it. The dark, absolute, spectral hue of Yomi, erupting from within her body! From that soul-tether, finer than spider silk, detonating outward! Yomi-giri. The Undying Slash. A single slash, arriving from ten thousand ri away.
And then, Kumo-Oni's body split cleanly down the center. The Soul-Chasing BowArm Transformation. Across a thousand, ten thousand kilometers, the question had never been whether he could strike. The question had only ever been what the effect of that strike would be after it landed.
He hadn't struck at Muzan's thousands of flesh fragments before, purely because the number was simply too vast. The distance, too great. No matter how strong Shinji was alone, he truly could not deliver a thousand, ten thousand slashes with a single lock-on. It was better to leverage the strength of the Demon Slayer Corps.
But now things were different. Only a single "Kumo-Oni" existed. And she had absorbed only a single residual sliver of the Demon King's blood. He could strike. And he could... kill.
In the final accounting, though Kumo-Oni had devoured Muzan's last flesh, she had also paid a price. To devour the Demon King as a demon herself, could not possibly come without cost. She was already gravely weakened.
But even so, even as she looked down and saw the fissure still spreading across her chest, saw that wisp of Yomi's light, his light, bleeding from the crack, Kumo-Oni, having grasped what was happening, showed not a trace of fear. Not even rage. She was still smiling. Smiling as she spoke.
"It seems… I am to die as well."
"How utterly ruthless you are. Truly… you have left nothing unaccounted for."
"But… to die by your hand… is also… happiness."
'What in the world had the Dark Spirit infused into this creature?'
Shinji's brow furrowed deeply. The new Demon King, born in the depths of the crevice beneath Honnō-ji, from emergence to annihilation, had not even lasted the span of a few minutes.
Tamayo, standing nearby, had been utterly petrified with shock. All that remained in that place, in the end, was a swath of pitch-black darkness. And, a single drop of "blood," like a tiny gemstone.
[Detected Cultivable Item: Residue of the Celestial Immortal Elixir]
[Quality: Divine Artifact (Incomplete)]
[Description: A legendary elixir crafted by an ancient being who journeyed from the distant continent to this island realm. In pursuit of eternal youth and immortality, the ability to freely transform the body, the union of Yin and Yang, the fusion of Sun and Moon into one, to achieve the pinnacle of humanity, the form of the ancient Celestial Immortal. Though flawed due to the absence of a certain component, it could still grant mortals a twisted immortality. Currently, only residue remains. Furthermore, it has been contaminated by the lingering 'obsession' of its final user. It can no longer be consumed. However, if its power can be activated, it may be possible to use it to split off and gestate a 'clone' of its final user.]
[Note: Though this specimen is exceedingly rare, it is not unique. It was imported from across the sea.]
Beneath the lock of the soul anchor, this was the final flicker of the System before it faded.