Chapter 00: Beyond the world

Part 1°

The shadow of death always stalked me with relentless persistence. From the moment my heart stopped beating several times in my mother's womb to the instant I was born, when doctors declared me dead, pulseless and breathless.

And just as I was about to be taken for cremation, I fought.

I fought with all my might.

I fought.

Until finally, I let out my first cry—a desperate scream announcing my arrival in this world.

I can assert without a doubt that my most fervent wish came true. But I could achieve it only with one body; that was my limit.

"Ubuyashiki, I hate to admit it, but what you said is true: every animal, every human, every living being that walks upon this accursed earth is destined to encounter death, without exception."

Feelings, on the other hand, are eternal and indestructible. I cannot recall a single person I've killed. Once the body dies, everything comes to an end.

But what about emotions? They are inherited, immortal. Even in that, I have lost.

Until I had the audacity to witness a reality that filled every fiber of my being with unparalleled emotion: Kamado Tanjiro.

Although my body is about to be pulverized by sunlight in a matter of moments, my dreams and feelings will remain indestructible. They will endure for all eternity.

And this young man, whose heart and breath ceased long ago, still harbors living cells. That means he is still alive.

I still have time, all the time I have left.

I will pump all my blood, all my power... all into you. If you manage to survive this imminent death and emerge unscathed, Kamado Tanjiro.

Kamado Tanjiro...

Kamado Tanjiro...

You, Kamado Tanjiro...

You will conquer the sun and walk beneath its rays.

You will become the most powerful Demon King, the strongest, the greatest in the world.

After all, you share the same blood as Kamado Nezuko. You are her older brother, and your unique lineage flows like thunder through the leaves.

In these final moments, I can see only you, brat. Tanjiro, my child, you will not die; I trust in you.

"Make my dream a reality, Tanjiro... You..."

You must destroy the demon slayers.

Part 2°

The city lay in ruins, a chaos of debris and corpses. The scene, grotesque and macabre, was littered with bloodied limbs strewn about. The tranquility that should have followed the massacre was shattered by a gut-wrenching battle cry.

"—ASSEMBLE!"

The few hunters who still clung to life turned their gazes toward the source of the shouts. Zenitsu and Inosuke, despite their exhaustion, raised their heads in alertness. This was no mere coincidence or mundane concern; something grave was unfolding.

Tomioka's words reverberated like thunder amidst the chaos:

"—TANJIRO HAS BECOME A DEMON; WE MUST KILL HIM BEFORE HE SLAYS ANYONE!"

A few meters away, Tomioka launched himself with all his might at Tanjiro, preventing him from seeking refuge in the shadows. The boy snarled and emitted an infernal scream as Tomioka's sword pierced his side, the skin searing under the sunlight.

"—KEEP HIM UNDER THE SUN UNTIL HE INCINERATES TO DEATH!" —Tomioka shouted desperately.

With tears in his eyes and demon blood staining his face, the Water Hashira held the sword with all his strength.

"I cannot allow him to hide in the shadows! If I had arrived even a moment later, that kakushi would have been instantly killed," Tomioka thought.

He closed his eyes, refusing to witness the death of his friend, helpless to prevent it. He blamed himself for his incompetence and miserable existence.

"Please, Tanjiro, return to who you once were," he silently pleaded.

The infernal wails of the boy echoed in his ears.

"—Just die already!" —Tomioka cried out in desperation.

His fists clenched tightly around the sword hilt, and tears filled his eyes as his body surrendered to the inexorable weight of fate.

Finally, he opened his eyes and looked upward, hoping to catch one last glimpse of the beloved Tanjiro. But surprise left him breathless: Tanjiro's dark blue eyes met his, pupils now dark red and slit like a feline's.

"Do... the sun's rays no longer burn him?"

Before he could process the situation, he received a punch to the jaw that sent him flying in the opposite direction. The demon, with supernatural strength, halted Inosuke's sweeping blade as if his arm were tougher than diamond.

"—What the hell is wrong with you?!" —Tomioka exclaimed.

Zenitsu, supported by another hunter, approached Inosuke, who pointed at the woeful Tomioka.

"—Tompamchiro! He's our half-and-half baori nakama! Did you hit your head or something?"

Ignoring his former comrades' comments, Tanjiro instantly regenerated all his wounds and burns. He assumed a threatening stance and launched a renewed attack against Inosuke with speed and strength beyond measure.

"No one can fight anymore. This is simply too much," Zenitsu murmured.

Tanjiro's irrationality and ferocity left him dumbfounded. What would happen now with Nezuko?

Tanjiro's transformation was a terrifying spectacle. His fangs, sharp as daggers, jutted menacingly, and the flame-shaped marks on his left forehead and right jawline resembled those of Muzan, the original demon. But there was a third, smaller mark descending from the right side of his head to his brow, a warning of his newfound nature.

His eyes, once brimming with kindness and compassion, now gleamed only with irrational hatred and brutality. The light that once reflected hope and determination had been utterly extinguished.

The blond boy, Zenitsu, could only relive distant images and memories of what Tanjiro once was. Those words echoed in his mind:

"We're all nakama, so we're like siblings. No matter the reason, if any of us strays down the wrong path, we'll stop them. We'll walk together no matter how difficult the road. We'll always be united in this."

Tears filled the blond boy's eyes as he recalled Tanjiro's words. He covered his mouth with his hand, pain reflected in his gaze. Without hesitation, he began to walk forward on his own, determined to prevent Inosuke from being killed.

"—TANJIRO, STOP!" —Zenitsu shouted desperately.

But at that moment, Nezuko unexpectedly appeared. She had regained her human form and lunged at her brother, biting his shoulder with force. Nezuko's fangs sank deeply into Tanjiro's flesh.

Zenitsu opened his eyes, astonished by the girl's foolish and reckless action. Meanwhile, Inosuke miraculously survived, slowly recovering as Nezuko distracted the demon.

"I'm sorry. I'm so sorry, Onii-Chan. All this time, I didn't understand anything. You carried the weight on your shoulders," Nezuko whispered, crying and embracing her brother tightly.

"Why do you always end up suffering, Onii-Chan? Why do kind people have to fight for survival?" Nezuko expressed her pain and frustration.

Clutching her brother's shoulder with closed eyes, Nezuko was unaware that what she considered her brother was about to decapitate her with his claws.

"—TANJIRO, STOP! IT'S NEZUKO! SHE'S HUMAN AGAIN, DON'T KILL HER!"

Zenitsu leaped onto the demon's back, struggling against him. But Tanjiro seemed to grow angrier by the moment. He opened his mouth in an inhuman manner, threatening to tear Nezuko's face off with a single bite.

"—GRAAAAA!!.."

Inosuke intervened, delivering a swift blow to the back of Tanjiro's head.

"—GRR, THIS AND GRRR, THAT! JUST SHUT UP ALREADY AND RETURN TO NORMAL!"

"—DON'T LET HIM HURT NEZUKO!"

Inosuke and Zenitsu grappled with Tanjiro, but he gained ground rapidly. Inosuke, tears in his eyes, drove his sword into the demon's neck, attempting to erase all shared memories.

Meanwhile, Zenitsu refused to accept the reality unfolding before him.

"—TANJIRO, YOU'RE A KIND PERSON, RIGHT!? RETURN TO NORMAL, PLEASE!"

But Tanjiro was completely unhinged. A bestial roar erupted from his throat, creating a brutal shockwave that flung everything within a 100-meter radius.

The city was enveloped in a curtain of smoke, a dense haze rising from the debris and corpses.

The vibration from the devastation was so intense that distant buildings collapsed, their existence shattered into dust and rubble. The air thickened, laden with the metallic scent of blood and desolation.

Amidst the chaos, Tomioka emerged from the whirlwind of particles, waving his lone arm as if trying to disperse the airborne sand.

Visibility was minimal; he could barely discern the shapes before him. Each step was a struggle against suffocation and uncertainty.

The scattered human remains and brain matter along the path were a horrifying sight. Tomioka, trained in the brutality of battle, couldn't help but feel a pang of pity at the magnitude of destruction. How many lives had been lost on this battlefield? How many dreams and hopes now lay shattered?

"—Tanjiro!?" —he cried out in desperation, his voice echoing in the eerie silence. —"Is anyone here?!"

The echo of his words dissipated among the rubble. Tomioka pressed forward, staggering, his vision clouded by dust and blood.

He remembered the fight against Muzan and the absurd amount of blood he had lost. But he couldn't stop. Not when his comrades' lives were at stake.

He Was Gone

Tomioka had no idea about the current state of the other Pillars. Most of them had been attended to almost immediately after the battle, but this new threat had separated them.

He clung to the hope of finding the others unharmed, but the silence surrounding him was unsettling.

As he advanced, the sobs of a girl grew louder—a heart-wrenching lament that seeped through the debris and desolation. Tomioka's heart clenched as he followed the sound, his footsteps echoing in the silence broken only by the groans of pain.

When he finally arrived at the scene, he could do nothing but collapse onto the ground, overwhelmed by the tragedy unfolding before him. The two hunters who had accompanied Tanjiro throughout their journey lay there, fatally wounded. Inosuke, the boar-headed boy, was notably missing his right arm, and a deep chest wound left him struggling for breath.

A few meters away, Jigoro's apprentice, Zenitsu, knelt over Nezuko. His chest bore a mortal wound, as if he had intercepted an attack meant for the girl. Nezuko, her eyes red and swollen from crying, looked at him with a mix of gratitude and desperation.

"He—he disappeared…" Nezuko stammered, her voice breaking. "I—I don't know what happened. Everything happened so fast… He…"

Tomioka didn't know how to console her. He had no answers, only a heavy heart and overwhelming helplessness. He glanced up at the sun, now a faint smudge through the dust and smoke. How had he vanished so quickly?

The kakushis arrived, moving with efficiency and seriousness. But Tomioka remained there, immobile, feeling the weight of defeat.

Tanjiro had escaped, taking with him all the hopes, all the efforts of those who were no longer there. The battle had been in vain, and loss hung over them like an insurmountable shadow.

Tomioka stayed sprawled in that place, unsure of what else to do. The sun, now hidden by the dust, seemed to mock his impotence.

All the fighting, all the camaraderie, all they had sacrificed… For what? Tears mixed with dust on his face, and in his heart, sadness became an irreparable wound.

Part 3°

"T-Tan…jiro!"

"T…T-Tanjiro!"

"TANJIRO!"

"You… don't belong… to them!"

"You're a perfect being!"

"A century has passed… and still they haven't found it!"

"The blue spider lily!"

Tanjiro's body writhed urgently on the damp, muddy ground, his eyes snapping open as he heard the mixed voices. He sat up immediately, his labored breathing gradually calming as he realized he wasn't in immediate danger.

"—Nezuko? Where… am I?" —he wondered aloud, scanning his surroundings.

Before him rose a dark and somber forest—a wall of twisted trees and thorny underbrush that seemed to whisper forgotten secrets. Sunlight barely penetrated the dense foliage, creating dancing shadows that played tricks on his vision, blurring the line between reality and illusion. The trunks, covered in black moss and entwined vines, appeared alive, as if they were watching his solitary figure venture among them.

Mist swirled among the trunks, obscuring the ground covered in rotting leaves and sinuous roots. A heavy silence prevailed, broken only by the wind's murmur and the occasional snap of a branch.

Taking a moment to introspect, he realized he was wearing his hunter's uniform—completely worn, scratched, with his right sleeve torn to shreds. His haori had vanished entirely.

Desperation began to take hold.

"—Nezuko!? Nezuko, where are you!? Nezu…!" —he shouted, his voice echoing in the forest's emptiness.

Anxiety surged; he could affirm that he had heard his sister's voice before opening his eyes in this strange place, but a headache and dizziness assaulted him as a torrent of images flooded his mind—images from a past that wasn't his own.

"—Ha, ha, ha!" —he gasped, trying to catch his breath. "—M-Muzan?"

Despite the dizziness, he managed to stand.

But the pain, along with the images of countless Muzans and the upper three moons flashing rapidly through his mind, caused his disoriented vision to spin three hundred sixty degrees. Staggering, he collapsed by the edge of a lake.

Exhaling wearily, he propped himself up with his arms, sinking his hands into the damp mud.

"—What's happening? Where are they all?" —His voice trembled; his gaze never left the ground beneath him. His foggy mind hindered movement.

In his first attempt to rise, a surprised groan escaped his mouth as he glanced at his nails—now sharp as swords. Shock reflected in his eyes as he looked at his own reflection in the water.

The lake mirrored a distorted but recognizable image: his face, marked by hatred and hunger, eyes reflecting a nauseating mix of amusement and delight.

His nails were long and pointed, almost like claws. This new detail intensified his sense of unreality, deepening his confusion and fear.

He sank back to the ground, his heart pounding in his chest. The ominous forest loomed over him, whispering dark promises and unfathomable mysteries. It wasn't merely a place; it was a living entity, a labyrinth of ancient secrets and dark power, twisted like the branches surrounding him.

"—What's happening to me?" —he murmured, his voice barely audible, echoing like a distant cry in the vast, dark expanse of the forest.

As he struggled to regain composure, an unnatural cold slid down his spine—as if the forest itself breathed, observing him, passing judgment.

Part 4°

Tanjiro's mind still resisted accepting what was happening. His body, however, told a different story. The physical enhancements and the disproportionate increase in his senses left him breathless, as if caught in a whirlwind of incomprehensible changes.

He had been standing for a while now, but the strength his body now possessed felt unreal and repugnant to him. His energy recovery was at an entirely inhuman level; his fatigue dissipated like morning mist. How could this be possible?

"My strength increased exponentially," he thought, clenching his fist. Veins popped around his arm, as if they wanted to burst through his skin. "I can feel that man's blood coursing through my veins like scorching lava…"

He had been walking for several minutes in this strange forest. He had no idea how he had ended up there. The twisted trees covered in moss were unlike anything he had seen in Japan. They seemed bleak and lifeless, as if time had left its mark on every trunk and branch.

Of course, he had encountered other forests. The one beneath Mount Fuji, for example. A dark and eerie place, full of secrets and dangers. He had undertaken several missions there and could assure himself that he would never return to such a place.

Then there was Mount Natagumo. Just thinking about those hunters hanging from invisible threads sent shivers down his spine. He remembered the desperate struggle, the feeling of being trapped in a deadly spiderweb. But that was different. Those were memories from his past life, right?

As strange as it sounded, he could recall the events with exact clarity. He could even perfectly envision the perspective of the thread demon.

Tanjiro stopped by a puddle, gazing at his reflection in the water. His eyes, more intense and inhuman than ever, seemed to search for answers in his own face. But all he found were more questions.

Who was he now? What did all this mean? And most importantly: where was Nezuko? The fog enveloped him like a dense mist, and his mind struggled to find a logical explanation amid this forest.

Any number of unknown causes could be swirling in his head if not for the event unfolding before him. His significantly improved eyes noticed a slight ripple in the water.

"Something big is moving," he thought, but he couldn't discern any shadow or object capable of creating such vibrations. He understood that something small wouldn't be capable of achieving this; only a massive or sufficiently large object could.

The wind continued to blow steadily, rustling his burgundy hair. Instinctively, he reached for something at his waist—something he knew how to handle well and that could get him out of any tight spot.

—…?

Right at that moment, Tanjiro realized his katana wasn't within reach. A small head emerged from the puddle beside him, startling him. It resembled a man around thirty years old, with disheveled, mud-covered hair obscuring his face. But what caught his attention first was the blood, and his sense of smell confirmed that something was amiss.

"—Sir!?"

Obviously, he received no response. The unmistakable scent of death wafted into his nostrils, and the situation grew stranger with each passing second.

Tanjiro shook his head.

"I apologize. What were you trying to achieve in this forest?"

Tanjiro's innate kindness and empathy surfaced ironically as he attempted to retrieve the body that, according to its floating position in the puddle, seemed to have submerged there.

"Move or die," echoed in his mind.

"Move or die."

"Move or die."

Curiously, the question of how the man could have ended up in that puddle never crossed his mind. Perhaps it was only the head? But that wasn't possible; demons typically devoured that part.

Why hadn't he wondered about it at that moment? He crouched down to pull the man's body out of the puddle but felt a pulse in his left hand.

"Death! Death! Death! Death! Move or die!"

He saw it coming, slow but inexorable.

His hands sank into the mud as he felt the man's shoulders. With a sidestep, he avoided the charge of a quadrupedal, humanoid creature.

Within seconds, more of those creatures emerged from everywhere: trees, corners, even from the same puddle where he had retrieved the man's body.

"—Demons?!.. No… They somehow possess a more… human-like life presence?"

But he couldn't truly discern differences between the two existences.

The first creature, the one that attacked him from behind, began to growl and emit strange moans, gradually advancing toward his position.

Tanjiro immediately went on high alert. Without his sword, he doubted he could escape this. His eyes scanned the area, searching for an escape route.

By fate or an unprecedented miracle, he noticed the Western sword hanging from the man's waist. The beast also saw it and leaped at him with a deafening roar.

"—…?!"

The scream dissipated in the air as a brilliant crimson blade sliced through the creature's neck like butter. In the blink of an eye, Tanjiro had taken the sword, and as he gripped it, it transformed into that same red glow.

Positioning himself defensively to protect the human's body, his red sword gleamed intensely, warning any of those creatures that approaching would lead to the same fate as their companion.

The beasts, witnessing how easily their kin had been killed, roared furiously but dared not move an inch. Their instincts screamed that the human before them was anything but normal.

After continuing to roar and with Tanjiro maintaining his stance, the beasts retreated and fled. They had lost their territory and their meal.

Feeling no further danger, Tanjiro released a relieved sigh as he lowered the man's sword to a less aggressive position.

"Activating the red sword just by grabbing it… yet this thing keeps moving, even after being decapitated."

Tanjiro advanced cautiously, his controlled breathing causing his chest to rise and fall steadily. His eyes, filled with sadness, focused on the lower part of the writhing beast in the damp soil.

He knew there was no longer life in that body—only a set of nervous mechanisms and natural muscle contractions persisting. In that moment, he could see it clearly: the creature's agony, trapped in a cycle of suffering from within.

His inherent kindness emerged once more. Determinedly, he raised the sword, ready to end the beast's torment.

With a precise cut to the upper spinal cord, he completely severed nerve communication, halting the spasms.

"May Buddha light your path," he murmured with closed eyes. "If you ever return, I pray you find a worthy life."

When Tanjiro regained his composure, his eyes opened slowly, as if they feared facing the reality unfolding before him. The creature lying in the puddle was an aberration—a grotesque blend of flesh and bone that defied all logic and nature.

Its skin, a mélange of gray and brown tones, was cracked and wrinkled, as if it had been dead for centuries. But it wasn't just the appearance that resembled demons; its bones and ribs twisted and curved, protruding from the skin like sharp blades. The long limbs, accompanied by claws, seemed sculpted by darkness itself.

Embedded deeply in the creature's skull were beads that once glowed with a sickly yellow hue. Tanjiro couldn't tear his gaze away from those vacant eyes, which seemed to have witnessed both eternity and despair in equal measure.

—"Its structure is very similar to newly converted demons…" —he murmured, his voice barely a whisper in the mysteriously charged air—"I wonder if…"

As he leaned in for a closer examination, Tanjiro noticed that only a faint trace of what had once been a living being remained. Pairs of bones were scattered on the ground, like pieces of a gruesome puzzle.

"I see," he thought, "apparently, they disintegrate upon death, but in a different way. Normally, demons vanish along with their bones, but these still linger in some form."

He chuckled nervously, the sound barely escaping his lips. What kind of place had he ended up in? What strange creatures inhabited this forest?

His gaze shifted to the body of the man he had rescued. He imagined this stranger being killed by these creatures, and empathy filled his eyes. Perhaps he had children, a family waiting for him, seeing his thirty-something appearance.

Using a wet cloth, Tanjiro wiped away the multiple bite marks that likely led to the man's demise. But it wasn't just that; the deceased man's attire intrigued him. Was he truly in Japan? The man's clothes—a leather shirt and pants—seemed sturdy and practical. Small pieces of metal covered vital areas without sacrificing mobility.

"I could say he's a hunter," Tanjiro reflected, "but he doesn't wear the uniform exactly. Still, the fabrics are almost the same material. Where on earth have I ended up?"

—"I'm so sorry," he whispered, as if the man could hear him. "I hope you don't mind me taking your belongings."

Finally, Tanjiro made the difficult decision to don the deceased man's clothes. They were slightly damp, but it beat being practically naked with his torn garments. The scarlet cloak billowing in the wind felt strangely familiar, and the lightweight armor underneath reminded him of his Demon Slayer Corps uniform.

His eyes fell on a medallion hanging from the man's neck. It was a robust, heavy jewel made of dark, lustrous metal, skillfully crafted. The unmistakable shape of the medallion caught his attention: a wolf's head with open jaws.

—"You hold a memory," Tanjiro whispered as he held it in his hand. "I'll make sure your legacy isn't lost."

Hoping to find an inscription that might lead him to a relative, he carefully removed the medallion. There was no visible inscription, but Tanjiro silently vowed to find a way to return the stranger's belongings.

—"Although I suppose I should first figure out where I am…"