Disclaimer: I don't own "Kimetsu no Yaiba" nor any references used in the story. Everything belongs to their respective owners.

"Hmm. It would seem that I have to find some use in you. For now, that is."

Those were the words Numa, known as the Swamp Demon, had first heard from the moment when that fourteen-year-old pink demon huntress had beheaded him.

With the voice that intimidating, Numa had no other option but to stay silent as time seemingly had to slow down as his head slowly reached to the ground.

"It will be only matter of time before I make my way to that world. A few weeks at least, perhaps a month or two should suffice for the time being."

"...Who are you...?"

The Swamp Demon uttered. It was the first thing he could up with that was appropriate for such a moment like this

"Ah, so it seems you are still conscious, demon. Normally in most cases when I'm performing this spell you wouldn't hear it... A fascinating discovery, I suppose."

Numa had no idea what the disembodied voice was talking about. But all he knew was that he felt an overwhelming power and authority as the voice replied after he made that remark.

"My name is Mordred, demon. I am one of many Nobles of Darkness that are under the service of the Lords. And I have a task for you to accomplish in my stead."

Before Numa could reply, he could see a cloud of darkness enshrouding his fallen body and that same cloud began its descent on him.

"Your task is to kill the demon with the Hanafuda Earrings. As for the girl that killed you, make her suffer."

The tone of the intimidating voice used, dark and emotionless, like the embodiment of all things in darkness itself.

Before long, Numa began seeing images of a human boy, wearing the same set of earrings as that traitor of a demon. He saw that same boy fought him nearly the same way as that accursed female Demon Slayer that beheaded him.

The surge of power was felt by the Swamp Demon. He felt he was twice as strong as before, as if he had eaten several times as many girls he had eaten in his entire demon life. A power he never thought he would possess.

"To accomplish that task, I decided to transfer your counterpart's memories of that world to yours. Including his strength. As well as a small gift."

He liked it, his newfound strength is amazing. Numa laughed menacingly at the power he was granted by the voice.

"Now then, demon. Shall we start? Good, a bid thee good luck. Abyssus Nirvana."

The cloud of darkness fully covered both Numa's head and his body.

Soon after, the Swamp Demon stood where he once fell.

Numa, the Swamp Demon, was given a second chance.

The cloud of darkness that enshrouded Numa and his decapitated body was by no means ordinary.

This mysterious phenomenon, as if it has never existed until now, was something that was reasonably correct for the Demon King to be cautious about.

Unknown to him, records of such event were written amongst the most ancient of scriptures that were hidden in the ages. Some were forgotten, others were nowhere to be found. Those that could salvage from ancient ruins that housed these scriptures cannot be deciphered by even the most modern of translators and translating devices.

But the name of the cloud of darkness still remained. It was depicted multiple times by those who had managed to get those ancient scriptures and its name was called "Darkening Enlightenment," or referred by its common name by its casters as it was called, "Abyssus Nirvana."

The exact mechanics of "Abyssus Nirvana," was unknown to anyone but the casters themselves. The ancient scriptures explicitly stated that "It was the most closely guarded secret that none, except the casters, will know thereof. And only those casters, who have the Lords' Authority and Blessings, are said to be able to use it to its fullest extent."

However, the Demon King of the Rising Sun, Kamado Tanjiro and his demon subconscious companion Kibutsuji Muzan, knew not of what the cloud of darkness could do. Nor they knew about the existence of the ancient scriptures that stored crucial information of this phenomenon.

The reason was simple, the ancient scriptures are from another world.

But Tanjiro, who had seen that cloud of darkness prior to the one he was now witnessing unfold before him was the one thing he recognized before. And it was recently before his transfer to this world.

"Mordred..."

It was the first thing that Tanjiro had uttered in recognition when he smelled the familiar scent that was in the cloud of darkness. It was eerily the same scent as that pursuer despite being visibly unrecognizable of its color when he used first used the See-Through World on him. But his scent was still ingrained inside of Tanjiro's mind

"Tch." the Demon King grunted in frustration. Feeling useless as he was forced to watch the cloud dissipate as it revealed Numa with his head now reattach to his body. And using both the See-Through World and his nose, he can sense that Numa was at least six times stronger than before.

It took a measly 15 seconds for all of this to happen.

The former Demon Slayer lightly flicked the sword's guard from its sheath with his thumb. Revealing a black-colored blade before it turned into a burning red crimson hue. A burning sensation can be felt throughout his body as he intentionally leaked a small amount of his power. A power that symbolizes his strength and worthiness of the title as the Demon King and the strongest Breath User of his generation.

Although he wanted to jump in immediately and kill Numa before anything bad happens to the two. But he couldn't bring himself to just recklessly when the matter of preserving this world's timeline is at stake. Especially when he, himself, looks similar to this world's counterpart of him.

He needed a disguise. That's what he needed.

But what? The haori itself is partially different, but I need something more... Unrecognizable in order to deceive Nezuko for a while.

He sniffed, using his abnormally enhanced sense of smell to find what he sought.

Then a certain, distinctive scent had made itself to Tanjiro's nostrils. With the Demon King himself turning back to the direction of the mansion in the distance.

"That will help," his demon subconscious companion suggested suddenly. The eldest Kamado wordlessly agreed with the demon as he flickered away. Leaving no traces of where the Demon King of the Rising was last seen.

The Sun Breath user hoped that both his sister and his counterpart in this world would be able to handle this on their own for the time being.

"Ah, no. Is your forehead okay?"

The Demon Slayer, Kamado Nezuko, second eldest child of the Kamado family, softy called out in concern as her finger reached to the wound on her brother's head.

It was still there, although it was a lot transparent than before. It looked like it was already healed. Was the reason her brother, who was turned into a demon, eats food now was to regain back his energy after it was used to heal the injury?

Nezuko let out a sigh, "I'm glad that you're fine, nii-chan."

Tanjiro, her older brother, let out a fond grunt and kept on munching. Nezuko laughed at her brother's childish act, happy that it only took a little effort for her to smile. Then her smile slowly vanished as she took a glance on his eyes.

It was ginger, it wasn't his original orbs, of course, as it was formerly a beautiful burgundy color. It was the original color he got after he was turned into a demon. Yet, Nezuko was sure, when she emerged from the disgusting swamp and immediately went to check on her brother, she saw the color of his eyes changed.

From the dull, dull, dull ginger to terrifying, appalling, horrifying yellow. How his cheerful expression and warm, warm, warm aura was gone, exchanged into something cold and empty.

Cold and empty as the truest evil of a demon who never regretted their actions, like the beast she just slew.

"Nii-chan," she uttered, garnering the attention of the ginger-haired boy. She looked at him with such intensity that he had to hold off of his usual eye-smile, "Will you promise me not to put yourself in danger like that again?"

The oldest was blinking in confusion at her request. But nodded anyway.

Then, Nezuko saw her older brother widen his eyes. Shock registered on demonic brother's face.

"Nii-chan?"

She looked in confusion before her older brother swiftly pushed to the side. Caught off guard of her brother's actions as she fell on the side where her brother pushed her.

Nezuko then heard a sickening crack. A sound that made her cringe in pain upon hearing it.

After she regained her bearings, she saw a sight she did not want behold.

"Nii-chan!"

She cried out, an overbearing wave of concern and worry filled her voice.

The pink huntress saw an arm impaled at her brother's stomach. Blood pouring in that fatal wound that would kill most people almost immediately.

Fortunately though, her brother was a demon. So a wound like that won't kill him. But Nezuko could not bear to see her older brother get hurt like that, let alone ignore like it wasn't there

If things could get any worse, that same arm retracted. Blood spurting out of the hole in her brother's stomach. Nezuko widened her eyes in horror and shock at the sight of it.

And as her brother was about to fall on the ground, a powerful force propelled on the far side of the street. So far that Nezuko could only see her only remaining family a small speck in that distance.

"Ha ha ha! This power is amazing! With this, I might be six times as powerful than before!"

Nezuko turned to the source of the voice, anger visibly shown on her face. But a mixture of shock and surprise soon took over as she recognized who the attacker was.

It was the Swamp Demon she had just slew.

"You!?" she exclaimed, drawing one of her two swords, "How is it that you are alive!? I thought I cut your head off!?"

This isn't possible! She thought, small drop of cold sweat started streaming down as a tinge of fear can be seen on her face, I thought he was finally dead. But how is it that he's alive?

There were two ways to kill a demon. That is, by either exposing them to sunlight or have their head cut off by Nichirin Blades.

The demon cackled in response, as if to mock her. And then he spoke menacingly.

"I admit, you did cut my head off," the demon admitted, Nezuko could not see the fog that told her a lie coming from him but the fog of truth was shown instead. Her eyes widen at the color seen at the Swamp Demon, "But that doesn't matter. All I want is to see you suffer and finally eat you. Of course, before doing that, as payback for cutting my head off, I'll make you feel a slow and painful death you will ever experience."

He declared with certainty. Nezuko saw the fog that showed her that the demon wasn't bluffing. He really wanted to see her suffer and die slowly by his hands.

She can't die, not without having her brother turn back to human again.

I need to finish this quickly.

With that she charged, her opposition stood as if without a care of the world.

She expected him to have some sort of plan but she saw the opening thread. Tightening as fast as she had seen when she had cut his other duplicates.

Time seemed to slow down for her as she saw her opponent standing still. Not once the demon moved.

Still, the opportunity lay before her. And she would not hesitate to do so.

"Full Focus. Breath of Water, First Form: Water Surface Slice!"

A single concentrated slash. The most basic of the Breath of Water styles. But certainly an effective move when all you had to focus on that single slash to finish things off.

It's over. The Pink Demon Slayer thought as the blade was about to reach the Swamp Demon's neck.

But to her shock and horror. The opening thread, which was seen and proven when it shows her an opening in the enemy that she can strike at, was suddenly snapped.

What?

With that single thought, eyes widen in shock as she could barely hear the demon utter. A smirk can be seen on his face

"Martial Demon Art: Fortress."

The unbelievable sight took Nezuko aback.

The neck she had cut before had actually blocked a hit from a full focus breath attack.

The neck should have been cut off under the force of a full focus breath attack had just been blocked head-on. Even if it had remained intact, the force she exerted should have made the demon knocked flying. However, it was Nezuko's sword which bounced away, like it had struck some ridiculously strong wall

Then the demon the followed up with his next move.

"Martial Demon Art: Focus Battle Aura."

His right hand glowed a crimson light. Creating a color Nezuko loathed at the reminder of the fog that made her seethe in anger.

Barely blocking the attack on time with her sword. Nezuko can feel her bones creak at the force made by the Swamp Demon as her feet skidded several meters away from her original position.

She felt her entire body shaking, her breathing heavy. Her entire figure reeling after the effects of the blow. How is it that he's so much powerful than before? And what the heck is a Martial Demon Art?

The second eldest Kamado shifted her stance. At the same time, controlling her breathing at stable levels. Regaining her composure as she cautiously stared at the Swamp Demon. The said demon simply smirked as he calmly walked towards her, ignoring the two civilians along the way.

"You managed to survive that, huh, bitch?" the demon cackled menacingly as he queried, "Though I must admit, I have yet to completely get used to this newfound power. But hey, we demons mastered our Blood Arts the moment we got them. So safe to say it wouldn't take too long for me to be able to use it to its fullest potential."

Nezuko glared at the Swamp Demon as she prepared for her next move.

Then she saw a familiar burgundy and black fog at the corner of her eyes. Charging the demon head-on.

"Nii-chan! Get back!" she shouted, her words fell on deaf ears as her only remaining family seemingly did not mind at her at all and continued his charge.

"Hoh? You're approaching me?" the Swamp Demon taunted, "Instead of working together with that human, you've decided to charge at me head-on!? Ha! I'll show you what I've got, kin traitor!"

With that said, Nezuko saw her brother about to deliver a powerful right hook aimed at the demon's face. With fierce force and velocity exerted, making Nezuko's own mean hook seem tame in comparison.

Then, she saw the same smirk she saw when her attack repelled. She couldn't help but feel the demon had something in store for her brother.

Her fears were confirmed when the demon sidestepped the moment when the blow was about to be delivered.

The Swamp Demon grinned as he grabbed Tanjiro's extended right arm.

"Take this, traitor! Martial Demon Arts: Ability Boost! Greater Ability Boost!"

With that, using Tanjiro arm, the demon had tossed Tanjiro over his shoulder and slammed him on the ground, hard.

The ground shook at the impact, making the Demon Slayer's demonic brother spat out blood. A crater was instantly formed right below the victim at the moment of impact. Showing the sheer strength and power the demon had seemingly put all of his might.

In an act of cruelty, the demon, still holding the eldest Kamado's arm in his hands, made a brutal stomp on Tanjiro's right arm. Making a gruesome display of a limb's removal as blood spurted out near the shoulder of the Demon Slayer's brother.

"NII-CHAN!"

Nezuko cried out, her vision red with hatred. Her fury can be clearly seen on her pretty face when she saw the person she tried so hard to protect was being tortured by the order demon.

"Get away from him!"

She charged, using her concentrated breathing to its fullest possible potential.

She retracted the arm she used to hold her sword as prepared to unleash the fastest Breath of Water technique in her arsenal.

Total Concentration. Breath of Water, Seventh Form: Piercing Rain Drop!

It was a fast and accurate stab. Like a rain drop piercing through the thickest defenses with the force of an armor-piercing round.

But, once again, the demon had another trick up in his metaphorical sleeve.

"Martial Demon Art: Gale Acceleration."

The demon moved. His swift movement was like a blur to Nezuko's trained eyes, the same eyes she used to survive her training with old man Urokodaki.

She wasn't fast enough to register her thoughts when something was thrown at her. Her sword piercing through the object producing the sound of flesh piercing as her body was pushed away.

Nezuko desperately tried to soften the blow the best she can do. She could feel her bones creak the more she tried to exert more effort as she skidded away from the Swamp Demon once more.

Again!? Nezuko internally lamented, this being the second time the demon was able push her back twice.

Then she came to a sudden realization on the object the demon used when he thrown something at her.

"Nii-chan..."

The red-eyed huntress nearly could not bear to utter the words of dread escaping from her mouth as she saw her brother, with her sword deeply piercing through his abdomen.

While the older brother had a look of pain as his usually normal expression contorted into something akin to suffering that not once she had seen her brother made throughout her entire life.

A burning feeling of hatred and vengeance filled inside her heart. Her eyes were glaring at the demon with pure fury that could be appropriately phrased as—

Hell hath no fury like a woman scorned.

—like no other word or phrase could come close to describing the burning emotion she has inside of her heart.

However, without warning, she could her left cheek feel a cold and unforgiving face as she felt body momentarily left the ground as she was briefly sent flying to the other side. Not knowing what had struck her.

She felt her body landed on the dirt ground with an audible thud. Her cheek was throbbing with a pain far worse than what she experienced when she was trained under Urokodaki and with Makumo and Sabito.

"Numa Right Hook! Ha ha ha! Nice name for a surprise attack, huh, bitch!?"

She heard the demon cackled as with her near blurry vision and she tried to stand up but to no avail.

Is this what it feels like to have in a receiving end of my fists.

She thought out off topic. Remembering the many times she had her fist performing her signature mean hook like the time when she and her brother encountered the Temple Demon, and that one time she had hit her would-be fellow Demon Slayer.

But her internal musings was soon replaced with a renewed hatred as she saw her brother embedded on a nearby wall in front of her. With her own sword clearly seen to have been deeply pierce through her brother's abdomen from the front to back.

"Ho oh? You want some more? Even though you're not strong enough to fight me anymore?"

The pink huntress ignored the demon's taunting as she drew her second sword from its sheath. Seeing that her first one being out of use currently...

She felt her body weak as it trembled from just holding her own sword. The aftereffects of the demon's fist had left her weakened, how the heck did she gotten so weak?

"...What did you do to me?"

Nezuko weakly queried, but her tone suggested otherwise as her hatred for the demon still fueled her burning desire to finish him off.

"Hoh? Wondering just now, huh? Ha! Not like I would explain my powers to a weakling like you."

The Swamp Demon's words made swift jab at Nezuko's feelings. Gritting her teeth at the mention of being weak.

Like the time she first started out to find the demon that killed her family and turned her brother to a demon.

She could just let the demon kill her and be done with it.

"Like I would just stand here and die while a demon like continue to kill innocent people like this!"

She took a stance, her weakened body was screaming at her to stop. Not wanting to overextend herself like this.

But paid no heed. Her anger was fueling her determination to fight at the end and not giving in to what was an overwhelming opponent.

"Even if it takes every sweat, every tear, and even my very blood to kill you! I will not let myself succumb to my weakness! Not now! Not this time! I will not let myself, my nii-chan, and other innocent people succumb to the sickness called despair!"

The demon looked at her unperturbed. As if her word were all bravado and without any proof back it up.

The two-horned demon shrugged as he spoke:

"Well, suit yourself, bitch. Nice knowing ya."

With the demon said nonchalantly, he then took a fighting stance that not once she had ever seen him do. She could faintly see the demon's upper body emitting light. And she could feel a massive amount of the released power the demon held back.

She could in nowise interrupt it and the Swamp Demon's raw power collided against her senses with overwhelming ease.

"Martial Demon Art: A—"

The demon was suddenly interrupted as she could see the figure in dark planted both his feet at the back of demon's head. With enough force to actually have the two-horned demon sent his entire body laying on the ground. Using the momentum he produced to perform near impossible aerial acrobatics as he gracefully landed on the ground with his back facing in front of her.

With the illumination of the moon above him. She could see the figure wearing a dark-colored late Edo Period armor but his body armor was partially covered with an odd haori with a green and black checkered on one side, and the other was pure black like the dark of the night. And she could tell the figure's head covered with a crestless helm like he had cut it off recently.

She then saw a katana with a guard that looks like fire inside its sheath tied comfortably at the figure's left waist. With the sword's handle calloused with near constant use.

She saw the figure turned his head and looked her wearing a seemingly ordinary faceplate that covered his entire face except for the eyes obviously.

But what surprised her the most was his cat-like plum orbs.

Then she saw his color.

A demon!

It was unmistakably a demon. The figure's color in front of her confirmed it to be so.

The intensity was far more than the demon that slaughtered her family and turned her brother into a demon. She nearly pointed her sword at him if it were not another side of the armored demon.

She was nearly taken aback at the sight of a gentle good shade of the demon's normally dark color on one side and the intense evil-like side on the other.

But the harmony of both shades was perfectly matched. Not one overpowering the other. Like it had accepted both sides of the same coin.

Who is he...?

The pink huntress wondered. She had never seen with a color of different shades. Her brother was only a mixed burgundy with the dark color of the fog that generally was seen on demons.

Then, the demon in mismatched haori spoke.

"Are you alright?"

The demon asked in a gentle tone that reminded her of the time when her older brother had used to speak a tone like this each time when he was concern of her well being.

But other than that, she feel something swelling inside of her. Like it she had found what was lost.

Then she remembered, the memories of her brother when he used to talk before he was turned to a demon.

She missed it. She missed it so much. The comfort brought by her older brother's reassuring voice, she horribly missed it.

A single tear formed in the corner of Nezuko's eyes. The memories of her once human brother resurfaced and brought an emotion that was recently experienced fifteen days ago.

Then she felt the demon's tekko (gauntlet) caressing her head in the exact way her older brother would always do when she was sad.

"It's alright... Don't worry, I'll handle this."

That reassuring voice, it was something her older brother had always said when he does things that were outside the scope that Nezuko was able to do.

"Who are you?"

She asked. Realizing she had uttered the words she wanted to reserve at the right moment.

Thankfully, the demon in samurai armor seemed to ignore her as he went to face the Swamp Demon as the latter was fully recovered.

"Who the hell are you, you bastard!?"

The two-horned demon angrily yelled at the demon samurai. Which the latter was eerily calm in the face of the monster that Nezuko was unable to deal with even with her demon brother on her side as well as despite being a strong Demon Slayer in her own right.

"I've been called by many names."

The samurai demon spoke. Speaking nearly nostalgically.

"You can call me whatever you want. But I like you to refer me by one of my stupider names that a certain friend called me at times."

She saw him shifting to an unarmed fighting stance. Nezuko wondered why he wouldn't he used his sword strapped at his waist. But she could feel that the demon in samurai armor was no slouch either.

Then, she heard him tell his name.

"You can call me Kamaboko Gonpachiro. Nice to meet you, Numa."

And cut!

Whew! Well finally this chapter is done. Hopefully I will get some sweet responses... Heh, heh.

Anyways, that's for my short Author Notes. If you like this story be sure to press the fav and follow button and be sure to leave a review.

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That is all, gabrielchiong11 out!