Disclaimer: I don't own Kimetsu no Yaiba nor any references used in the story. Everything belongs to their respective owners... Except for Mordred and Yuna, I own those guys.

Kibutsuji Muzan, the demon that had terrorized Japan as the "Father of All Demons" for nearly a millennia, was having an unpleasant night.

It all started when he was minding his own business with his human wife, which he learned she was a widow with her former husband that had died tragically in the closing days of the Great War in the European Front at the spearhead of the latest offensive as a brave and valiant soldier serving for his Emperor and the Empire itself, as well as his daughter who was an extremely young child; who barely knew her birth father back then.

Of course, Muzan doesn't completely care about them, but he did consider them not worthless since their company was anything but boring with the woman and her daughter gave him enough amusement to not kill them outright. Safe to say, they were one of very few humans who were unknowingly close to the current Demon King and not considered useless.

Then that girl with those damn red-eyes, the eyes that a certain older brother of his strongest demon had once looked at his cat-like ones with an emotionless look, had appeared out of the blue with her demonized brother in tow.

He growled in utter disdain, reminding him the eyes of the man who had nearly took his life a mere four centuries ago during the Warring States Period. The man who wielded a Nichirin blade with crimson color as bright and powerful as the sun. He was the only human in his time as a demon that caused so much great fear in his indefinite life.

Fortunately for him, he sent two of his strongest non-Demon Moons he had in his disposal. Ordering to kill the girl and bring her head to him.

He suspected the girl to have the same blood as Yoriichi, the man who was claimed by the Demon Slayers before erasing him from their records as well as by his brother as the Strongest Demon Slayer of his time and in history, something that girl scared him.

Speaking of the man's brother, he claimed that the man's purpose for slaying demon's was to avenge his wife and newly-born (or still at the womb, or whatever, he wasn't sure Kokushibo's information was accurate to begin with) child. He doubted that Yoriichi had the will to remarry another woman and bang her to have another child... That would unfortunately have to die in the same incident as the first.

Come to think about it, does he have the will to have another family after his beloved wife and child been murdered to begin with?

It was a thought that came to him with sudden interest. Something he hadn't thought of after all the time he needed to recover his wounds inflicted by the man. And it was... Out of mere curiosity he hadn't considered to be a possibility, to matter how extremely slim it was as he cupped his chin in mere contemplation that it could've happened centuries ago that he wasn't aware about.

Maybe it was that subconscious thought when he first visited the Philippines on a whim. And one night with the Upper Moons, he was met with several demons that weren't of his own.

At the time, he was perturbed and perplexed that there were demons who were not of his blood. It irked him greatly until he met that one demon among the group, and he was easily the most powerful of them all. Even dwarfing his strongest demon, Kokushibo who was Upper Moon One, and on par with his own.

Eventually, the two found themselves fighting each other, with his Upper Moons watching him fight against the demon with the demon's companions watching him fight against him, Muzan, as well, it would seem that their fight was akin to a duel more so than an actual war. And it was a duel that would determine who was the better demon.

After fighting what it seemed to be an eternity (when it was just eight hours in total) until the leader of the demons announced it was a draw. Admitting that he, Muzan an outsider, was powerful as he.

He pursed his lips as he admittedly at the time that the demon leading the group was indeed as powerful as him, even matching at full power as the other demon fought him on equal grounds.

The Demon King that terrorized Japan grew to respect him as the leader of the demons who was also the Demon King in the land Japan now controlled as their own.

He was elated to hear that he was transformed into a demon was a healer that Muzan suspiciously suspected to be the same one that transformed him to be the demon he was now today. And it grew as he discovered that they were of the same year since the two were strip of their humanity.

It was by that time he offered the Filipino Demon King an alliance. A mutual defense treaty between two demon kinds.

The Demon King of the recently conquered land from the Spanish happily agreed, with certain conditions such as conveying information via their own right handmaiden; which Muzan learned that they both have right handmaidens which increased their respect even more to each other.

And soon, an alliance had been made on that night. With two Demon Kings with each other's respective Demon Elites.

A little more of a decade later, shortly after the official annexation of the Korean peninsula despite Prince Ito Hirobumi reluctance of such politica movel, came with another member who was also a Demon King of Korea and joined in on their merry alliance and it was soon renamed as the Triple Entente from the Dual Central Power alliance name. Inspired from the alliance that some of the Great Powers of the West had called themselves in defiance of the Central Powers who were also Great Powers themselves as well.

It was more than a joyful times that the three genuinely got since all them were turned into a demon via some mysterious doctor. And they made sure their alliance stood mightily against any adversary. Especially when they heard reports from their respective demons that the Demon Slaying Corps had grew in number, recruiting the local populace of the territories the Empire of Japan had gained since the Meiji era.

Although it may big news, but it did not matter to them. Especially since their demons had already joined forces and had mutual understanding of each other. So mutiny between the demons of their respective lands was practically nonexistent if the strength of the alliance's leaders continued to be unquestioned.

Muzan grew to respect them as comrades and brothers. And it made him happy that he made such good friends between Demon Kings of their respective lands.

Back to the girl, now with the girl being, hypothetically, a descendant of that man; he had no choice but to kill the pink-wearing demon hunter, which surprisingly a girl around fourteen years old. But then again, he had killed a number of those girls around her age personally, especially they were lucky to have encountered him and unfortunately no people around them. So he had made quick work ending them literally in less than seconds.

As he was musing from the girl having slight resemblance to Yoriichi to him killing girls around the age of the supposed descendant of that man, he felt a sudden overbearing presence just above him.

He stopped, feeling a pressure only demons around his and two others level in the Triple Entente, that could've exerted such power just by their mere presence alone. And he was familiar with the feeling before.

Muzan scowled, as he turned his back and faced an unfamiliar figure standing behind him in the empty alleyway where he killed three unfortunate civilians who were unlucky enough to piss him off in his already bad mood.

He was met with a sight of a figure with a height on par to the demon hunter's brother, his choice of apparel was a complete set of dark-colored Samurai armor that was partially covered by an odd haori with checkered black and green on side and completely dark color on the other. Crossing his arms, while making sure that he wasn't open for exploitation.

The near millennia old Demon King wasn't too sure if the figure in front of him had a poor taste in fashion compared to him, but he did notice a pair of plum orbs that looked like that of a cat's staring at him notifying him that he was a demon. With an aura of dignity and authority that only him and two other leaders of the alliance could certainly compare in strength.

Then the samurai demon spoke.

"So we finally meet, Kibutsuji Muzan."

Yuna sat in the distance on top of an abandoned building at the edge of town, staring at the illusion-covered building with a bored look on her face, having an uncharacteristic attitude from what she displayed earlier with her father and Muzan around.

She sighed in exasperation, showing her true personality at the boredom of waiting two demons her father mentioned to be Susamaru and Yahaba. The sheathed sword her father gave her to use was placed on her left side but close enough to grab and unsheathe the blade within just in case of an emergency.

The second child of Kamado Tanjiro wished that she would just go into that cloaked building, eavesdrop whatever conversation the demon woman Tamayo and her student Yushiro had with Nezuko and her father's counterpart. Something about the cure of turning back demons into humans if the timing of their conversation was anything to say about.

She noticed the group had arrived at the building hours earlier than what her father had experienced prior. Considering that he left Nezuko at the park and the man that cooked the noodles basically demanded to eat them but her father's could not since she was demon unlike her father's counterpart who eat human sustenance as a means of restoring energy.

Another deviation, Yuna mirthlessly thought as she continued to count the time for the arrival of the two demons who were strongest of the non-Demon Moons that Muzan's counterpart in this world, as well as her father's world version of the near millennia old demon, had in his disposal.

However, she knew based on her father's memories, which was inherited intentionally since her birth in order to know how to combat any situations which involved accomplishing any orders given by her father based on his memories, knew that there were supposedly six occupants in that building. Any more of that number would drastically deviate the timeline her father and Muzan was fixated on stopping from going out of control.

Luckily, she had enough common sense to learn from the memory, even if it displeases her a bit. Pouting cutely at the mere thought of it.

As the minutes went by, Yuna began to wonder what was like to be human.

Since she was born of the parting of her father's flesh, independently shaped by her own volition unconsciously, powered by the gift of her creator's blood granting her power that made it as her own. Many could consider as the perfect being as she was created by her father's image. The ultimate lifeform.

Yet, she felt she was incomplete. She had yearn for something that a human emotion called love could perhaps satiate her desire. And yet once more, she felt there was something to it other than that. It would be a bit cliche if love was the only thing she yearned for.

She looked at her nonexistent chest, an envious emotion rising inside of her as she saw countless women with sizes much more apparent than hers. Wondering if she was born as a human, would she have a bigger and more apparent figure than what she as?

Yuna frowned, knowing the line of thinking she right now was wrong.

Although shapeshifting might be the answer to her... Assets problems, she, unfortunately, lacked the ability to perform such a power only her father and that old demon Muzan seemed to be the only demons capable than her to do so. Even her older brother seemed to achieve it to a certain extent.

She slumped her head, her chances of having anything that resembled anything like the many women she seen was second to none. Releasing a sigh in acknowledging that she'll be like this, even at True Demon form, which was the most powerful a demon possessed when accomplishing certain requirements that Demon Kings and Queens and their spawns seemed to have in common.

Her musings were cut off as she sensed a presence of two demons. Stalking the empty street, searching for certain people that caught their interests or by the orders of their client.

One of them was has a short black hair and was crawling on the ground. The big, blue marbles on his neck jingled as he moved, his green-black yukata was a pulled a bit from the ground as if he didn't want to get it dirty, which was odd for her. He raised his hands and at both of his palms exists an eye each, with a green sclera and red-eyes with a black arrow as it pupil. Yuna noticed the eyes somehow sniffed, as if catching up the scent that was long gone.

"Can you see it."

The companion of the demon asked. Yuna could see that it was a girl, a bit younger than the previous, with black hair and red highlight at the bottom. She was bouncing the colorful kemari ball, making her black obi that covered the orange kimono swayed, following the gravity.

If it weren't for the ring, ring, ring, the ball sounded, as it created a beautiful yet ominous sound in this dark nigh without stars. Se would've stared at the noticeable bumps the female demon's clothes seemed to modestly cover.

If she hadn't, she would've looked at her own and nearly teared at the comparison alone.

"Of course. I see footprints. The boy wearing a uniform turned around there and circled a long way around. And then there were two other people and one of them is wearing a huge box. Looks like that one is our target."

The boy with eyes on his palms, snickered. Crazed manic undertone seeped from his voice. His real eyes were still closed as if he preferred to use the one on his palms to see, staring at said footprints.

She was wondering if it was the work of his Blood Art. If it wasn't, she doesn't know what it is.

"How do we kill them, ufufu?"

The girl giggled like a happy child. Even if those yellow eyes with horizontal pupil, Yuna could easily sense that they were radiating with madness.

"I feel this power coursing through me. Because we received the blood from the Great One just now~"

Is she talking about Muz-chi now? Ugh, thinking about her drinking that old fart of a demon's blood is just gross.

"Well, it was obvious right?"

The innocent quirk of lips of the boy turned sharp, pointed fangs peeked beneath the demented smirk.

"We are going to slaughter her as cruelly as possible."

That was when Yuna had enough of hearing as she stood where she sat. Leaping at great distances while performing aerial acrobatics that many would've consider her as veteran professional of her career, landing gracefully while intentionally alerting the pair as they turned their backs in order to see her.

"Who are you?"

The boy demon with closed eyes demanded. He and his companion cautiously shifted their stances at the sudden arrival of someone that they did not expect.

Yuna responded, her action surprised the duo, with a greeting.

"Hello there. Nice evening we have here, I'm Yuna, nice to meet you."

She gave them a warm smile, with the two demons sent by Muzan having perplexed looks on their already confused expression.

If she were going to keep this world from deviating from her father's world, she might as well have some talk with them, including to kill some time off to keep her away the boredom of waiting.

Tamayo, the demon lady that helped her and her brother from the incident earlier, had explained a step by step she believed will help her creating the treatment to turn back demons into humans.

First, she wanted to investigate Tanjiro's blood.

Nezuko's mentor, Urokodaki Sakonji, had theorized the reason why her sibling was more human than demon was because he is an older brother, a protective older brother at that, even when he lost his memory, his instinct to protect the youngest was there so he knew not to attack Nezuko. They had taught him not to attack innocent civilians too. Just because those people are not his siblings or family, doesn't mean he should abandon them. Sakonji said he's practically a toddler since he was turned into a beast, mimicking everything he saw.

Yushiro scoffed at that half-baked theory — too full of optimism and sentiment — yet he didn't outright deny it. Saying that, sibling theory aside, the amount of blood Tanjiro received or, maybe, the blood-relation itself play a part in it. In which Tamayo agreed.

Second. She wanted to gather the blood from demons with Kibutsuji's blood coursing through their veins as much as possible.

The doctor surmised that Tanjiro was currently at a very rare and very precarious stage of development. She explained while observing the ginger-haired boy, who was now playing Nezuko's hair and making new sets of braid from it.

That was also the reason why in their previous battle, her brother went a bit... Deranged.

The human side was buried for a while when his emotion when his was in a jumble. And the demon side sleeping within took over, making him a lot stronger yet a lot crueler. This was easily explained by the changed of eye color.

Demons sometimes undergo drastic transformations when they were turned into the said devil; a good example was the green demon from the Final Selection mountain ground. He had a human appearance before he turned into that disgusting form.

Tamayo didn't know it was a fact or a rumor, but if you have dark coloration when you were still a human, if you do undergo changes, the color will turn lighter when you're a demon, and possibly the other way around too.

Yushiro is a good example of that, as his hair was full black when he was human yet now turned half-lime. In Tanjiro's case, the lighter the color was, the more he loses his memory and his humanity along with it.

Because the beast who turned him into a demon was not the nice Tamayo but the evil Muzan.

The ginger color is dull, dull, dull and Nezuko hated it.

However, if this information is indeed correct, then the theory of him retaining more of his human side than the demonic one was now confirmed. Because ginger is a lot closer to red than yellow. And her sibling's previous color is burgundy. Meaning, if you put it in numbers, his scale of transformation was under five than over it.

Meaning, that Tanjiro might become the key to unlocking the mystery of the man-eating demons in the future.

"The second thing I want from you is very cruel one." Tamayo lamented, head bowed, "The demon with thick Kibutsuji's blood coursing in them are demons that have... Gained a massive amount of strength from Kibutsuji himself. It won't be an easy task, robbing these demons of their blood. Even so—"

"—Are you willing to accept my request?"

"You don't have to ask for my confirmation on this, Tamayo-san. Of course, I will."

The demon hunter in pink haori promptly answered without hesitation. Her hand reached back and managed to cradle the demon brother's cheek before she continued.

"If you managed to create and manufacture the medicine, not only nii-chan,the lives f even more people — be it humans or demons — will be saved right?" she gave he a grin, "This may sound like I'm copying you but I've been wanting to turn other demons back to human too, the moment I promised myself to cure nii-chan. Demons were humans, they have their own emotions,. Am I right?"

Tamayo blinked at the firm declaration, blinded by the sincerity in it. Then, she smiled.

"Yes. You're right. Thank you, Nezuko-san."

Tiny and faint, yet so beautiful Nezuko actually blushed.

...Yushiro's expression was outright murderous, it made Nezuko actually sweat.

"I doubt it would work like that, Nezuko-sama."

It was an instant reaction. Tanjiro's nose twitched. Yushiro's eye widened.

Nezuko had an a confused expression on her face as she suddenly noticed on the corner of her left eye that somehow Yushiro and even Tanjiro were suddenly seen lying on the ground, tied from the hands to feet, their eyes covered by a white blindfold and mouth gagged by the same clothed. With her older brother had his nosed blocked by a wooden clip.

It was happening so fast, she did not have the time for her mind to register on what was going on. How the heck did it happen?

And she was met by a beautiful young girl around her age with the same hairstyle as her late mother, her skin white and as beautiful as snow, wearing a dark silk kimono that looked extremely expensive, with a black haori with swirling red clouds at its tips.

"Now, we have to discuss about... The medicine, shall we?"

"Hey, Yahaba."

"Yeah?"

"You ever wondered why we're here?"

"It's one of life's great mysteries isn't it? Why are we here? I mean, are the product of... Some cosmic coincidence, or... Is there really a God? Watching everything? You know, with a plan for us and stuff? I don't know, Susamaru. But it keeps me wondering every single day."

The hazel-eyed demon looked at her partner with a surprised and confused look on her face. Awkward silence ensued at the response her comrade had made.

"...What? I mean, why are we out here, tied to a stupid tree by some ridiculously powerful demon we don't know of?"

"Oh. Uh... Yeah."

"What was that stuff about God anyway, Yahaba?"

"Uh... Hm? Nothing."

"...You want to talk about it?"

"No."

"You sure? It isn't like you to stop like that."

"Yes."

It was in that particular night that two demons that were recently gifted by Muzan's blood were tied up into a tree with Yahaba's eyes on his hands were blindfolded by multiple white cloths that had managed to restrict his Blood Art from activating.

The ropes used to tie them were somehow reinforced, even with her, Susamaru's, incredible physical prowess, seemed to have no effect to even budged or snap the ropes open.

And it was like that for quite some time.

And cut!

*Laughing menacingly like a villain* Hope you guys enjoy this chapter 'cause the next one would probably be my personal favorite. Hehehehe...

That is all, gabrielchiong11, out!