Published in 12/13/2020: 7,203 words.

Edited in 12/25/2020: 8,885 words.

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

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

Those were the words uttered by the newcomer, who had appeared without them knowing, and had made herself known in a complete, and surprisingly, sudden fashion that it took both her and even Tamayo by surprise. And by surprise, she meant caught off guard.

Nezuko looked at her, bewildered confusion made known to her exposed expression, as the newcomer took her sweet time staring at them with a somewhat amused look with her cat-like eyes with the color of plum began to survey the room. As if she was confirming something based from memory of some sort. And that was the Pink demon slayer had realized, after seeing her color, that the newly arrived girl was a demon.

On top of that, Nezuko had just noticed that the recently-arrived demon had somehow tied both Yushiro, and even her older brother for some reason, so quickly, she couldn't have notice something had happened in that time. Confirming that she was no ordinary demon to begin with.

Though not knowing the exact reasons as to why she tied the two male demons in the room, she had some thoughts about Yushiro but never about her older brother since he had been with her throughout the whole journey after their family was killed by Muzan.

But her speed, the way she tied Yushiro and Tanjiro so quickly and unable to react to it, was what made Nezuko wary about the demon.

It was fast. Far too fast for her to react. It was almost as if it was like that time when both Gonpachiro and Numa had fought a few days ago. And she knew the two combatants from the town she visited prior to Asakusa was a whole another level. Far stronger than she initially thought of when she faced a certain demon back at the Final Selection.

And if anything, the demon's fog depicted her to be overwhelmingly stronger than Numa. Who, at the time, was far stronger than both her, Nezuko and her brother, Tanjiro, could hope to match. Especially with his use of the strange ability called "Martial Demon Arts". An ability she did not know even with the lessons and several facts told to her by Urokodaki. And that was the same demon who had been decimated by the poorly-named Samurai Demon that wielded a Nichirin blade, of all things, was toyed with from the very beginning.

The second living Kamado began to shudder subtly at the thought the person that recently made herself known had the speed to outmatch her senses and the strength to overwhelm her with frightening ease. Especially when she did it with casual ease.

And Nezuko knew the last demon who performed such a feat had struck fear into her heart and her very being. Fear that she would die before she could even react at all was absolutely terrifying for her. Even when she thought she could handle anything that could be thrown at her. It would seem she overestimated her own potential.

It was by that fear she began to remember the Samurai Demon. The demon who had intervened with the Swamp Demon, which she managed to learn his name was Numa, and easily bested the demon with overwhelming ease. As a result, she began to find respect for demons who had retained some semblance of their humanity, especially with the poorly-named demon who she first thought as an enemy but was with no doubt that he… Comforted her like he knew she was in pain.

And it was that time she had learned that there were demons who are far stronger and faster than both her and her older brother could ever hope to be.

Nezuko began to contemplate if this demon was on the level as Kamaboko Gonpachiro (gods forbid if that was the case), and she began to check the silk kimono-wearing demon's fog using her Sight to see if this was anything to do with Muzan trying to get rid of her or something similar of any sort.

The red-eyed Demon Slayer blinked her eyes twice, then thrice, as if she had just discovered something that she hadn't thought was possible.

Kamado Nezuko was born with the ability to see the Colors of the World. With it, she can see the colors that signify, or at least identify, the person or object based on the color of the fog she sees.

For instance, she could see a dark blue fog, she could interpret as the temperature of the weather of a single night would be a lot colder. And she used at times when it was useful for the people around. Mainly her family of course.

Prior to her training with the former Water Hashira, she could only see the fog of their defining color and their relationship with other people based on their similarity in color. If they're a family member or in a relationship, their individual color will intertwine and change. The best example of it would be when her mother had lavender fog as her color when she was still single. Then it turned to red-burgundy the moment she married her late father, who had red fog before, and stayed at that even after he passed away. A mark that she later knew that it meant that they were truly meant to be.

But now, she could track their last place, where they've gone and what were they doing by looking at the fog circling around. Like a trail left by an animal. Or perhaps the string of fate, if you're into the superstitious or romantic belief based on what interpretation you wanted it to be. But Nezuko herself was leaning on the latter due to reasons she was personally interested in. After all, she was still a girl at heart and she her own preferences to begin with.

If anything, she could see that the demon's color in front of her had the same color as her brother. The color that meant she was—

Burgundy… the same color as Nii-chan.

She thought in amazement, the color she had longed to see for the last two years since they left their home and buried their loved ones from the beast that slew them and transformed her brother into a demon. And it was that very likeness Nezuko wasn't sure if the pretty demon (with hairstyle similar to her mother of all people and admittedly has beautiful porcelain skin color) was related to either her or her older brother to begin with.

A distant relative, perhaps? She thoughtfully mused in her mind. Wondering how another member of the Kamado family, who she didn't know she had relatives to begin with, became a demon like her brother. She speculated in her mind to be the same case as her brother, but that was thrown off as the demon in silk kimono did not have the same mentality as Tanjiro's, who has a childlike personality.

But what shocked her wasn't just that, she was flabbergasted at how controlled her fog was, how powerful it is compared to the demons she met prior to Gonpachiro's first appearance. And it was significantly more powerful than Numa, the same demon who had overpowered her before, was compared to her.

And to make things much worse, her fog suggested that she's no slouch in fighting. And, in fact, a far better swordswoman compared to her.

"Could I ask, who are you? I suppose you're here for a friendly greeting, are you not?"

Nezuko's musings were cut off as she heard Tamayo's voice, which had a tone of hostility subtly hidden in her usual kind words with a hint of curiosity, in which Nezuko had barely managed to catch on. Much less the rage and fear hidden beneath the calm visage physically projected by her.

Using her Sight, the ability to see the Colors of the World, Nezuko could see Tamayo's fog wrapped in tense hostility slightly marred by fear and a tiny bit of rage as if she recognized the power the newcomer had despite not showing it directly.

In comparison, the newly-arrived demon's fog had showed that she had complete control of her emotions. Calm as the still pond in a windless, cool day in a middle of the wilderness.

It would seem Demons had a way to recognize who is strong and who is not.

The Pink Demon Slayer thought as she watched in silent contemplation at the two demons as the Kamaboko-level threat, which she categorized her based on the level of strength from the aforementioned demon, slightly tilted her head as if in confusion.

"I wasn't aware that you didn't know my name… That was to be expected, I suppose. I was sure that the old fart would've know of that unless he knew of your connection with Yoriichi-san centuries prior to this day. Especially when you decided to create a concoction that would ultimately lead to reversing a human-turned demon and the cause of a would-be certain demon's unfortunate demise."

She said in a matter-of-fact tone, but Nezuko could see a fog that depicted that she was partially lying, and the same time, partially telling the truth. It was hard which is which due to how jumbled the fogs seemed to depict, despite her the only user of such skill.

Who's Yoriichi? The Pink hunter wondered, vaguely recalling the name from her late father from one of those very rare nights he muttered in his sleep. The name of a person whom she could barely remember at the time. The name that brought such significant importance that Nezuko didn't know until now.

On top of that, Nezuko noticed that Tamayo was visibly taken aback, which the Pink hunter's curiosity on the name had further increased. The rare case of a desire to know who the person was and what kind deed did he or she had to make Tamayo, the demon who she learned to be capable of resisting eating human flesh and drinking human blood, to remember such things based on the name of the person alone.

Who was this Yoriichi that made her react like that?

"You… how did you know all about this? Especially him… Of all people?"

Tamayo was slightly shaken, as if the name alone had brought memories Nezuko wasn't sure because it was her first time seeing a fog with so many mixed-emotions that she almost swore that she saw a tiny of fondness in that fog at the mention of his name.

"I know a lot of things," she replied to the demon doctor, as she began to sat on the tatami mat on where she first appeared, not bothering to move from her spot as if claiming as her own, "With one, the ginger head boy over there had the same the earrings as his, and it was obvious that it clearly belonged to him. Who else would've worn an old decoration that smelled preserved and antiquated throughout the centuries worn by that man? Also, it was very obvious that judging by your intervention with the incident earlier with the almighty demon, it would seem that you had a debt to repay to that man in some way or manner. Whether it be to his descendant or to his spiritual successor."

She said, retaining the tone she said from the start, turning her head to the spot where the ginger head boy demon was tied. With the Demon Doctor nearly gritting her teeth showing her bare fangs, and with Yushiro violently struggled to break free from his bindings and uttering something gibberish due to his mouth gagged by the cloth the demon with plum-colored cat-like eyes seemed to used had some sort of overwhelmingly reinforced material.

It would made a very comedic scene if it weren't for the fact that no one was laughing at his expense in the first place.

"It's useless," she told to the lime haired demon, with an oddly satisfying smugness that Nezuko could see based on the seemingly younger demon's fog, though not showing outwardly, "No matter how much strength you put in order to break free from the ropes, don't bother. I've made sure it would be enough hold off even the strength of a Lower Moon. If you need to, just be as strong as an Upper Moon if you have the slightest chance of beating me and, less likely, standing on equal grounds against a certain old fart when he decides to go to his 'True Demon' form."

She said while ending her words with a smirk, as if she had done a deed that was planning for quite some time. A questionable action that the Demon Slayer hoped to know in the future in some way or another. And it made Yushiro more agitated than before.

Little did Nezuko know, from the demon's perspective, Yuna did it with the reason that payback for all for the things Yushiro of the previous world did to Tanjiro a few years back. And she did it in a sort of karmic way that the Yushiro of this world did not deserve.

After all, she possessed her father's memories. And whatever little grudge her father had in his overwhelming kind heart, she inherited the same way her older brother, Taka, had so.

And she would use every opportunity she has with the lime-haired demon whenever she can.

But there were three words that caught the second living Kamado's attention. And that was the only thing she managed to utter subconsciously.

"True Demon form?" she thought out loud with a curious tone, which caught the attention of the demon in silk kimono and Tamayo herself.

"Nezuko-san," Tamayo uttered, as if in disbelief from what she heard from the Demon Slayer, which caught the hunter herself off guard, "You do know what is a 'True Demon' form, right?"

Nezuko looked at the demon doctor in confusion, how the heck she was supposed to know that? Even Urokodaki-san didn't know or, at the very least likely, didn't mention it. Even if he did, it would've been common knowledge already to her.

"Do you know as well, Tamayo-san?" she asked the Demon Doctor who shook her head. Unintentionally confirming the subconscious feeling inside of Nezuko's mind that Tamayo did not know as well.

"Good grief," Nezuko heard the younger demon woman muttered audibly, "As should have expected, you two don't know anything. Including the lime-haired demon at the back as well."

Yushiro, who had been agitated earlier, squirmed aggressively in his restrained state at the mention of his hair color. But the demon with a sword, which Nezuko had noticed just now at the side of the demon's waist, gave a smug look at him before turning her attention back to them. Ignoring the Demon Doctor's assistant once more.

"Before I tell you what a True Demon form is, please let me introduce myself. My name is Yuna, nice to meet you Nezuko-sama, Tamayo-sama."

She made an extremely respectful bow at the hunter and demon, which the former was surprised how dignified and graceful she looked as she made her introduction. The way she moved was not anything she seen before. It almost as if she had done so in instinct and, maybe, trained to do so.

"Eh? You know my name?"

Was her exclamation of the demon, who she now knew as Yuna, suddenly knew her name out of nowhere. How the heck did she know?

"Oh? Was that a surprise?" quipped the younger demon, "I heard your name multiple times from your conversation with Tamayo-sama. Of course, I know your name. It was based on the fact that I knew the Tamayo that betrayed the demon she once served," the Demon Doctor flinched at the mention of her name, "and it wasn't that hard to guess that it was your name since you're the only girl, other than Tamayo-sama of course, in this room. Don't tell me I wouldn't know of that fact when I tied those two over there?"

"S-Sorry!"

She apologized with her face bleating red. Embarrassed that she somehow underestimated at how smart and perceptive Yuna seemed to be at a glance. And her deductive ability seemed to be on par with her intelligence.

She then realized, when was the last time I was this embarrassed?

Was it before her family were killed and her brother turned into a demon? The time when she first made her blunder when set out to a nearby village and had made a mistake?

Those were the times she almost forgot. The times that were simpler than it is currently. Oh, how she missed those peaceful days where she did not have to know the death and gore she witnessed in these years that passed after her family was killed by Muzan.

She balled her fists, the ever-increasing rage boiled in her heart at the devil who took her family and turned Tanjiro into that is no longer considered as human. Gods, she will kill him. She will never forgive him.

That was before she received a painful slap to the face. So hard that it echoed throughout the whole building they resided.

"You know, I can smell your hatred over here. It's disgusting, it's like smelling burning waste in the open field. If you don't stop it, I will give you that same slap if you ever thought of that again. And next time, after that, you will feel a much greater pain."

The voice of Yuna reached into Nezuko's ears as she looked up, holding her aching cheek where the slap landed, as she saw her with a disappointed expression. As if her expectation of the slayer did not seem to match.

Why is she looking at me like that!? Why is she making that look!?

Despite being to see the Colors of every living thing, she couldn't comprehend why this stranger of a demon, whom her Color showed that she knew what she, Nezuko, had experienced. Why was she showing empathy towards her? Why did she have to say those painful words to her? And to what right she has made to punish her like that?

These thoughts continue to swirl inside her rage-induced mind. Unable to calm herself down at the words the younger demon had made. The words that pierced her heart to what was essentially normal for people like her to feel.

Once more, she received another slap in the end of her cheek. Stinging Nezuko's face by the first and then the second slap Yuna struck at her.

"As expected, you have less control over your anger. Your brother was way better at this than you at controlling your own anger."

Pupils dilated and eyes widen in shock at the statement that sounded fact than opinion as she stared at Yuna whom the latter kept an aloof attitude. Clearly showing who was at control here.

"I'm sorry, Yuna-san," the pink hunter apologized as she calmed down, "It wasn't like this, I'm sorry."

"Hmph… That is to be considered. You have all that rage bottled up inside your heart, but your capacity to hold it in was nowhere near as your brother's. But, even in his overwhelming kindness, even he had his rage-induced moments. When he does, he is like a vengeful demon hellbent on revenge. If I were to compare, yours is much tamer than his. And at the same time, yours has the potential to surpass his one day."

Every word Yuna uttered, it struck Nezuko's heart more times than it should've had. Not used to verbal criticisms on an emotional level. Even Urokodaki, in his harsh training, was nothing similar, even with her time with Sabito and Makomo, was nothing to compare when her words struck harsher than she thought from a complete stranger like Yuna. Whom she did not know where she came from and to what degree she knew who she was.

But—

"My brother… You kept mentioning him. How do you know about him?"

It was bugging Nezuko when she first heard Yuna kept mentioning of her brother like she knew him. It was something Nezuko wasn't aware of. Is this demon a stalker?

She noticed Yuna's fog began fluctuate as if taken aback at the words she spoke. Like she was unintentionally spilling vague truths about her brother and her apparent knowledge of him.

"That… is for another time, Nezuko-sama. I'm sure you understand… that I'm not comfortable in telling you, yet."

Indeed.

She saw the Color of her fog, she was indeed not comfortable of her telling her, but why? Was there a reason not to?

"I'm afraid we've gone a bit off topic." Tamayo said, intervening between the conversation of the hunter and demon. "Now, were you going to tell us what a True Demon form is or not?"

Tamayo's words brought Nezuko's thoughts back to the original topic at hand. She nearly forgot after all the things Yuna said before the dramatic shift in tone beforehand.

"You are correct, Tamayo-sama. I apologize for the inconvenience. Now, what it is you like to know about first?"

She queried, as if expecting that it was a question and answer session for both the Demon Doctor and Hunter.

The first to respond was, obviously, Nezuko.

"What is a True Demon form? I heard you mention it a few times and it sounds quite powerful."

"Indeed. True Demon forms are, in simpler terms, demons who had reached the ultimate state of evolution. The pinnacle of their power. It is a form only Demon Kings, once they met the necessary requirements, can access to. It is an incomprehensible power only they could wield as their own."

She explained, with Nezuko shuddered at the mention of "the pinnacle of their power" a form that sounds as if it was a legendary status only certain beings have access to.

Then there was another line she felt that needed to be addressed.

"You said it was a form only Demon Kings have access to? What do you mean by that?"

That was what she wanted to know. Demon Kings. Does that mean that there were demon royalties out there? But wasn't Muzan the father of all demons? Isn't he supposed to have created the entire demon race on his own?

Then she got her answer. The answer she did expect to be the same as she initially thought.

"Yes, Demon Kings. They are demons on the same level as, or greater, than Kibutsuji Muzan. Whom you know him as the 'Father of All Demons'. Which, by the way, was partly true as he created the demons back since the Heian Period."

"Partly?"

"Yes. Muzan is the 'Father of All Demons in Japan' and to confirm your suspicions there are more demons outside of Japan. Whether you like it or not, this nation is not only one filled of victims with demons. In fact, the entire world is filled with them, there is no nation on this world that has no demons on it."

That revelation shook Nezuko to the core, there were more demons out there? With more innocent people suffering at their hands?

The thought made her sick. To think there more of those monsters out there that weren't created by Muzan but another demon entirely. How many of those Demon Kings out there?

"H-How many are out there? The Demon Kings, I mean."

Nezuko asked, a sore bump on her throat appeared at the mention of the words "Demon Kings" and she felt sick about it. Just the name Demon Kings has already her stomach churn as she imagined a group of demons with the same ability to transform humans into demons. Creating more of those monstrous creatures that threaten mankind.

She felt a chill in her spine as she imagined as to how many demons out there, outside of Japan and her Empire as a whole. The thought alone made her think that many people suffered in their hands.

Tamayo, in her perspective, seemed to be on the same boat as here, she was as surprised that there were other demons that weren't created by Muzan and shook her more than Nezuko. She had her suspicions when there was a lack of activity around these parts of the Kanto Region. Especially when she heard occasional news of the increased death rates at the Philippines, Korea, and Sakhalin in the past decade alone. It would seem there were other demons that were not created by Muzan, whom she loathed for these past centuries, had been those individuals who held the title of "Demon King" of their respective lands.

But the question was, as Nezuko mentioned, how many are out there?

When they got their answer, it was grimmer than they thought it would.

"If you count every nation there is, whether it be a colony or an independent one, there are at least one of each of those locations that housed them. Japan, the Empire as a whole, has three Demon Kings living and breathing today.

"What!?"

The exclamatory reaction of both Nezuko and Tamayo was astounding. Never did they know that there no just one, not two, but three Demon Kings here, alive and roaming to create demons as they want throughout the Empire Japan has created in the decades after the Meiji Revolution.

"Y-You mean to say there three Demon Kings, including Muzan, out there!? Throughout the entirety of the Empire!?"

Tamayo let out a barrage of words that spoke of her utter shock and horror, much to the surprise and shock of Nezuko, who she thought it was out of character for a demon like Tamayo to be like this. But then again, she hates Muzan as well.

For Nezuko, the mention of having three Demon Kings was absolutely horrifying. She had a personal vendetta against Muzan, of course. But to have two additional Demon Kings adding to the fray, had made the difficulty rating of her journey to kill all demons that attempted to harm innocent people skyrocketed to unbelievable levels. Finding Muzan alone is hard as it is, but the two additional Demon Kings was not something she could possibly handle. Even with the help of the entire Demon Slaying Corps, it is still impossible to face what was essentially the progenitors of demon kind of their respective homelands.

As for the Demon Doctor herself, she was absolutely livid. After all these years, those centuries of plotting Muzan's demise when she planned in creating a concoction that not only turned Muzan to human, if that were to fail, but to utterly weaken him to the point that the Demon Slaying Corps would have a fighting chance against the demon. But it would seem she was wrong in this case.

She already had trouble trying to create one specifically for Muzan, but the two Demon Kings, whom she knew nothing about, was making this harder for her. And creating a concoction for those two would take years, if not, centuries to know if they're anything like Muzan. But she speculated that the two Demon Kings might not know Muzan at all.

It was optimistic at best, but she couldn't stop the foreboding feeling that it wasn't the case. For all she knew, they might just be acquaintances with no real motive to be assisting each other.

But she was proven wrong as Yuna answered.

"Yes, including Muzan, there are, in total, three Demon Kings. Each with a unique set of powers, and all three had made an alliance. A mutual defense pact, with extremely good relations with each other, if you will."

The room grew colder at each words Yuna spoke. It was as if every word she uttered had dropped the temperature to an unbelievable degree.

Then the girl demon continued:

"The name of their alliance is called the 'Triple Entente'. Originally, it was supposed to be called the 'Dual Central Powers' 22 years ago as there were two of them at the time as it first formed. But, with the arrival of a third Demon King, the one can be found on Korea, making contact with Muzan ten years ago. The name of the alliance is changed to what it came to be as it is called today since Muzan had made that particular Demon King a member of their alliance."

She spoke monotonously, as if the information she gave them was nothing sort of common sense. A piece of information that one could easily get a hold of which baffles both the hunter and doctor at how she spoke in a rather casual but informative tone she used to tell them.

But for the three, including Yushiro who heard everything despite being gagged and tied up, was silent and could not believe that it was all true.

For the Demon Slaying Corps, they made it their duty to slay the demons, and ultimately Muzan himself, at all costs. The organization that existed for centuries and it was pretty clear for Nezuko that they weren't aware that there demons outside of Japan. Heck, they might not even know how handle them when the organization at question has already have their hands full in dealing demons that were in Japan alone. Since the members of the said Corps were a few hundred at best, with very few surviving the Final Selection.

If they had that information, Urokodaki would've told her of that with the two years she stayed with him. It… somehow confirmed her suspicions that the Demon Slaying Corps did not know of this at all.

In Tamayo's perspective, she was not, in the very least, elated at the news. In fact, it served a huge deterrent for her plans to destroy Muzan, and hearing that the two Demon Kings had good relations with Muzan does not bode well with her at all. The fact that there were three working together was something anyone wouldn't dream of possibly happening especially with the personality Muzan has before she betrayed him. And it was the worst possible scenario that could have happened.

They took a few minutes to let the information seeped in as Yuna, while waiting for them, stared outside of the window from tatami mat she sat on. As if she was contemplating deeply on whatever musings she has in her mind.

Although she didn't physically project it, but based on the Color of her fog, she was worried. It was almost if she didn't want to stay for too long. And yet, there was hesitation but then showed she complied to. Was she telepathically talking to someone? If so, then who?

Nezuko did not know who Yuna truly was or she was a friend or foe, but what she does know that she was here for a reason. For what?

The pink hunter's curiosity of this mysterious demon was great, and it did not take long for Yuna to turn her attention back to them. Noticing the interest Nezuko held in an instant, based on the spike of her fog flared in that instant.

"Now then, since you now know what a 'True Demon' form is and the existence of other Demon Kings, are there any more you want to know?"

She looked at Nezuko expectantly, almost as if she knew that she was going to be mostly the one doing the asking. Which, was frankly true as she did most of the questioning.

I swear, she's reading me like an open book and I don't like it.

Nezuko thought in disdain, pondering on what she was going to ask before there was one thing came to mind. And it irked at how perceptive the demon before her was showing.

Then, she asked the one thing she wasn't able to tell to a certain sword-wielding demon.

"Yes, there is one… Yuna-san. What do you know about Martial Demon Arts?"

Kamado Yuna, daughter and second child (creation) of Kamado Tanjiro, the Demon King of the Rising Sun, was the type of person who you call an ice-cold hearted demon. In reality, she was not.

She was the kind who takes things calmly as possible. Analyzing on what to do before acting on it, an intellectual fighter if you will. But, in the end of the day, she was just a three-day old demon whom her father created out of necessity for gathering information. Needless to say, at a glance, she was like a tool only used by her father but not to the extent that he didn't her as a person. Far from that, actually.

Even after turning into a demon, Kamado Tanjiro was a kind-hearted boy who was thrown in a world of man-eating demons and his once primary goal was turning his little sister back human and kill Muzan to avenge his murdered family. As such, he didn't treat her like a tool at all, but merely a father asking his child to do things with an option to accept or refuse his orders. To which implies that she has free will to take upon the words of her father.

Yuna narrowed her eyes, looking at the girl in front of her, who is actually her aunt, her father's younger sister, as she stared into her eyes unwaveringly. Like she was a threat that cannot be taken lightly.

The question of coming up with Nezuko's ignorance of what Martial Demon Arts were was part of the realm of possibility Yuna thought was expected to have placed since beginning of their interaction. After all, Martial Demon Arts were a special ability found only in the west. As such, she knew from the very beginning her "Aunt" was going ask that question. Even then, she also considered the probability that would ask that question later on.

But what she found strange is, Why now? Surely there is a better time to ask that?

For all she knew, it might be out of mere curiosity. She knew Martial Demon Arts was mentioned in her battle against the Swamp Demon before her father intervened. However, she already knew that sooner or later Nezuko would find out all about in some months after she became the Demon Queen.

As for the very reason why Yuna assumed her aunt of this world would become a demon was very simple. If she followed the very footsteps her father had taken during his time as a Demon Slayer, then there is surely a chance the same thing could happen to her as well. There was a saying in the west that history tend to repeat itself eventually.

After all, she and her father planned to keep things going on the right direction based on the evets that occur on their world. As such, it was a bit of consideration on their part as the events occurring in this world is similar to what had previously happened before.

The youngest "child" of Tanjiro let out a sigh, which had a visible effect on her aunt which showed she was on edge by that simple action.

Was her aunt usually like this? Based on her father's memories she inherited, the answer was simply no. But, in this world, and considering she was trained by Urokodaki, a brutal and strict trainer mind you, as that might be actually the case as it had been less than a week she left the former Water Hashira from his humble abode of a mountain and began her journey as a Demon Slayer. Then again, there was also the events that happened during her first mission as a slayer which ended nearly a disaster because Mordred had revived Numa and made him much stronger than he was supposed to be.

With that said, she responded with:

"Why do you want to know about Martial Demon Arts? I suppose you've met a demon that could use one, yes?"

Yuna queried to the only human in the room, who, in response, nodded. Confirming that it was from the experience she had with Numa the Swamp Demon.

"It's not my place to tell you that, Nezuko-sama." She answered, much to the young layer's dismay. "Martial Demon Arts is a power that exists solely in the western world. There is little to no chance that you'll ever meet a demon with Martial Demon Arts that you could find in this country. Unless, you're asking me for the sake of information, am I correct?"

She queried once more with the Demon Slayer giving the same nod as her response. That gesture irked the young demon as she had no recollection of her father's memories ever seeing Nezuko giving the silent treatment.

By all things under the Shinto gods, why does she smell like she's plotting something? Was her aunt that manipulative? She may or will never know.

"Very well. To be honest, there's too much of a mystery that surrounded Martial Demon Arts, even using the simplest terms would understate the true power of Martial Demon Arts used exclusively on the western world. I hope you understand that, Nezuko-sama."

"Yes," Nezuko replied, shifting a bit as if the answer Yuna gave to her was simply not enough, "but I want to know if there's a chance that the three Demon Kings, including Muzan, was aware of such power? If anything, I just want to know, that's all."

Yuna narrowed her eyes at the 14-year-old Demon Slayer, whose intentions were genuine enough to remove some suspicion.

"…They are aware. During the Great War, in years 1915 to 17, in the invasions of German New Guinea and Micronesia, both Muzan and the Demon King of the Philippines, Fidel Manila, whom the latter changed his name to suit in this modern era, visited both the annexed and occupied areas on a whim. With the Korean Demon King left to oversee his allies' respective homelands in their stead."

"On a whim?" The human Kamado asked perplexedly.

"Yes. Although, there were slight intentions on going to those territories under the assumption of meeting a Demon King on the area based on both their first encounter of each other 22 years ago. To which they are correct on their judgement."

"…Who did they meet?"

She asked, feeling a sense of foreboding nervousness creeping up in her spine at the thought of there was another Demon King that Muzan and the two other Demon Kings meeting at a secluded area. As of which Yuna could tell by her scent alone which the younger sister of her father did not know of that fact.

Then, she answered her. And it came with the young Demon Slayer widen her eyes at the unexpected answer Yuna made.

"His name was Makarov Kuznetsov, the Demon King, or Tsar as he wants to refer to himself, of Russia. A master of Martial Demon Arts of that western country full of rife from the civil war a few years back. The first western demon Muzan had ever encountered at Karafuto Prefecture up north of Hokkaido, in late 1917. To which he and Muzan negotiated diplomatically to share the hunting grounds of that island."

As for how she came up with the information regarding all of these despite being in this world for a scant few days. There was a simple answer to it.

She, and her father, had been relaying this information via their mental link in two separate locations. One of which is where her father was talking with the Father of All Demons in Japan.

Her father and the Muzan of this world had a rather healthy discussion between each other as fellow Demon Kings, which surprised the former since the Muzan of their world did not possess this trait. As of which the Muzan of this world was surprisingly fond of communicating with demons who are equally or more powerful than him as he knew the political world of the secret society of demons in different nations as he was informed that he, and the amount of demons he and his companions of the merry Triple Entente alliance had created, it boasted to have one of the largest demon population in the world. Just behind the amount the Demon King of Britain, which controls a third of the world's total landmass and its demons.

In short, Muzan of this world was considered to be as one of the Great Demon Powers that ruled a part of the world of their respective nations. Simply put, it was the landmass and the amount of high quality demons that Muzan and two others had amassed that placed them high on the ranking spot of the Great Demon Nations. Which the term created during the Age of Imperialism in the 19th Century.

That particular part surprised both her, her father, and Muz-chi himself who did not even know the existence of the Demon Tsar back in their world.

Her father and his demonic subconscious companion had underestimated the difference of this world had than their own world. Which makes things much more complicated than they previously thought since discovering that they weren't on their world but with a different chain of events.

For Yuna herself, she understood the gravity of the structure that this world balanced itself differently from the previous one. Resulting in one, if not, the greatest surprise that the world they are in are vastly different in comparison. Contrasting to what they knew and what it was impossible to have ever happened in the same circumstances.

An example of that was the Muzan of this world was—

"Tell me, Nezuko-sama, do you know how powerful that demon, who I am assuming to be the Muzan that you're currently hunting down, really is?"

She uttered the query aimed at the young slayer, who had just broken out of her stupor from the shock she received from the revelation that a western Demon King have made contact with Muzan just three years ago. The Demon King of a nation that the Japanese Empire defeated 15 years ago.

The Kamado slayer of this world recovered shortly thereafter and replied:

"Yes, I am aware. I can see the strength of his fog was dark and overwhelming. But nothing compared to Kamaboko-san, a kind demon I met a while back before meeting with Tamayo-san, whose intensity was far greater than Muzan's… Why do you ask Yuna-san?"

"…"

She stared at the pink-wearing Demon Slayer with a… Disappointing look sporting on her face which promptly made said slayer and the Demon Doctor widening their eyes at Yuna's expression.

"…Please forgive me, Nezuko-sama. But, have you… Properly gauged the true extent of his power?"

"Wha—?"

A wave of overwhelming killing intent soon washed over the room they were occupying— no, the entire building seemed to have been overwhelmed withh.

The ginger-haired counterpart of her father squirmed violently from where he was tied down and was desperately attempting on breaking the bonds that was restraining him. But was unsuccessful in his endeavor in doing so.

The other tied down demon in comparison was shooting glands of cold sweat from every pore of his demon body. Absolutely terrifying the poor demon who had never experienced this overwhelming pressure he was forced to feel wash over him. Drowning him in a way he wasn't used to.

Tamayo herself was extremely terrified and uneasy of the murderous intent that was continuously washing over them like a tsunami. Flooding her senses with absolute fear that she hadn't felt in a very long time since the day she betrayed the one who turned her into a demon.

For Nezuko, this was an unexplainable fear and despair clouding her eyes, which could see the Colors of the World, with untainted darkness that she felt something was blinding her. Unable to see the world in nothing but absolute darkness.

For Yuna, she—

"This power… It's just the same as…"

Father in his fullest, unrestrained power. So this is—

The daughter of Kamado Tanjiro audibly whispered, the last part unheard by the others. The other occupants of the room looked at her in shock and fear as they registered what she meant by that.

"Is this…"

Nezuko managed to utter those two words. Those two words that Yuna combined with her own, answering what was not clearly the case they had in mine.

"The Demon King of the Rising Sun, the undisputed leader of the Triple Entente alliance of demons. Kibutsuji Muzan, so this is the extent of your power… Or perhaps a mere fraction of it, I suppose."

Yuna uttered the words that struck the chord of two demons and a single humans to their very souls. Now knowing whose overwhelming killing intent came from. And she knew exactly where it had been.

"You're meaning to tell us that—!"

"Yes. That was from the demon, the Father of All Demons in Japan, whom you are attempting to kill. And it would seem that was him showing off his true power just now."

The Demon Princess, daughter of Kamado Tanjiro, cut off her aunt's words before she could say anything else. Which resulted in said relative with an dumbfounded expression plastered on her already tired body, who had yet fully recover from her battle with Numa. Which honestly surprised Yuna a bit.

If anything else, Yuna was aware the pressure just now, was the result of the combination of three different bloods from three Demon Kings merging into one.

A Demon King's blood was extremely toxic, a single drop could potentially destroy every cell of the ordinary human body. Poisoning them in a very painful death as seen during the final battle on that fateful night that destroyed the Demon Moons and the progenitor of all demons in Japan.

Those who managed to survive it became demons. However, the strength of the demons came from the amount of blood in proportion given by their Demon King. The more blood a demon received from the Demon King himself, the stronger they are. Which is no different from the Korean and Filipino Demon Kings.

But there was a limit to how much blood a demon could possibly take into their bodies. Those who had a far higher upper limit eventually made it to the top and the privilege it has as a high-level demon which soon became an elite group specifically made by their respective Demon King. The best example of that was Muzan's Twelve Demon Moons

There was a question that arose regarding this. What if a Demon King would receive blood from another Demon King?

In the previous world, Tanjiro had not heard nor witnessed such an action had taken nor it could have possibly happen. His travels and experiences in different nations, in different continents, that housed their respective Demon Kings had not done such a thing. Most of which are not aware of the other Demon Kings' existence, save for a certain amount found in the European Continent. But, even then, they did not attempt such actions, as their methods of creating demons in said western continent was vastly different than what was found in Asia.

However, in this world, Muzan and the two Demon Kings he had made an alliance with, had done what was essentially the impossible.

Somehow, in some way, the Muzan of this world had managed to take in the bloods of his two fellow Demon Kings into himself. Merging his cells with two other cells with vastly different structures than his own. Which there is no doubt that it could kill Muzan if he made a single misstep on his part.

And in a way, he had done the impossible. Taking in not just an amount one could measure by cups, but all blood that could be found in a Demon King's body that can be transferred to a fellow demon especially on the one with equal footing.

And it's procedure was similar to the way Muzan from the previous world had done to her father, resulting in making her father the ultimate lifeform. A true successor of the previous Demon King of the Rising Sun.

The Muzan of this world had taken in every ounce of blood from two Demon Kings and survived. And in doing so, received a power that was beyond man's imagination.

Not only that, the two Demon Kings attempted the same procedure as Muzan's. Which resulted in both of them surviving the highly toxic blood of Demon Kings. In turn, making them equally as powerful as Muzan.

To make things worse, they are as strong as her father in his True Demon form and in his full power.

"Tch."

Grunted, the princess made an audible reaction that restored the senses of the people she was currently meeting. In which it resulted—

"Ah, it would seem it had worn off… How annoying."

She uttered in a way that Nezuko, who had recovered her senses for the umpteenth time, looked confusedly at Yuna at what she had meant before turning to the only males in the room who were standing there with broken ropes can found on the floor.

Before Nezuko could properly react to this, Yuna spoke.

"It would seem that my Blood Art had reached its time limit. Compared to father's, he has no such limit. Amusingly enough, those two are quick to take advantage of that limitation."

She said so vaguely, enough for Nezuko to wonder who these "father" and "two" this swordswoman of a demon was referring to.

Then, in an instant, she found herself to be in the same place she had taken, even in the exact same position her brother took as well in an unbelievable perfect setting, just before Yuna came in.

"I have a simple request. Please handle the battle to come with the best you can."

Those were the last words Nezuko heard from Yuna.

And at the same time…

Tanjiro wrapped his hands around her. While Yushiro went to grab his teacher while shouting:

"GET DOWN!"

BAM BAM BAM BAM!

Before something crashed through the building, bouncing off the wall, floor, and ceiling. Crushing every single object it has touched.

A kemari ball rolled to a stop, making a nice, short jingle.

RING…

And cut!

Whew! Had fun writing this, so much so that it had taken this long…

Although there some things that wasn't explain as much, probably give it the chapter 4 treatment, might increase the word count by 2k at least.

Thank you all for this fic, finally reaching 100 follows. I greatly appreciate it.

Edit: Could I request a challenge? If so, I hope you do so.

It will take place in the mountains of Austria in the winter of the 1920s where the MC is a girl 14 years of age. You will design your OC as you see fit.

This is essentially like the beginning of Demon Slayer but with a twist. Like all of her family is dead with no survivors. With her becoming a demon.

Although she retained her memories and her mind, she has no recollection of the demon who turned her into a demon with Icy Blue Cat eyes.

Then she began to secluded herself in the mountains for like a month when she discovered that she was killing humans subconsciously. Where she begins her solitude and her self-consciousness of the actions she did not intentionally done so.

And during that month, she then encountered a Demon Slayer, a European version if you will, and attempted to kill her with no mercy despite her pleas to atone for the actions she done subconsciously.

With the Demon Slayer making his final, killing blow to her, the OC screamed and you know who comes and rescued her. Thus beginning the story as an apprentice of her savior and this where you will ultimately have to make from this point onward

That's all, I hope you will accept this challenge, and be sure to PM me if you accept it. gabrielchiong11, out!