Chapter 1: Prologue

Asakusa is a place notorious for its crowded and adaptive citizens, filled with machinery and life. The improvement of technology is the reason why the place was so bright and brimming with life. The emperor's efforts have brought human technology very far.

However, even the best places to live have their own set of problems, and this is not a normal circumstance of a 'high number of thieves'. This case is morbidly different, the problem comes from the high number of people missing lately, with no trace of their whereabouts.

For around two months, there have been reports that missing victims have appeared on the doorstep of their families as no more than a decapitated head, with perfect cuts around their neck and no blood left inside of them.

Yui couldn't be more delighted by watching their horrified faces from the shadows.

That and her elusive nature earned her the nickname "The Ghost Demon". Quite fitting for her style to murder people quickly.

She wouldn't have been able to do this on her own, it was all thanks to Muzan Kibutsuji's kindness that she was able to gain the means to do so. He granted her a power she never knew existed, an unimaginable power that enabled her to accomplish incredible feats.

Without his help, Yui would still have been living with her abusive parents in a poor village. She would have to bear her weakness as a frail human for the rest of her life. No more. Now, she will do what she wants. No restraints. No rules.

Her method of killing was very simple. Since the alleys of Asakusa were very dark, nobody could see her overall monstrous appearance, only her silhouette. In the shadows, she seemed like a relatively tall woman with a long kimono decorated with flower ornaments.

At night, people - especially men - want to enjoy life as much as possible. Eating food, getting laid, and gambling. In the streets of Asakusa, men who have stooped low will do anything for pleasure. Men like that are not willing to pay for a highly expensive oiran on their night. Instead, they seek those women unfit for the oiran houses, those women relegated to the alleys. There, men can have fun for a relatively cheap price.

"N-No please, l-let me go!" a man begged as he tried to remove the hand that clenched around his throat.

Sometimes, men aren't so lucky. Red eyes, sharp teeth, cracks on both sides of her face with veins bulging from her throat. All of this masked with her lustrous long silver hair.

"But why, darling~?" Yui grinned as she wickedly licked her lips. "We're just getting started, right, right?!"

"Damn, monster!" the man snarled as he swung his fist at full force, hitting Yui's face hard. She recoiled back not from the pain, but because she was surprised by the fact that the man showed resistance.

Satisfied that his punch connected, the man grinned victoriously. Women were easy to break after all.

Yui didn't move for a while. However, she didn't lose her grip. In fact, she made it tighter to the point that the man started to gargle on his own blood as Yui's nails pierced his trachea.

"You actually went out of your way to hit a woman..." Yui whispered, her tone no longer carrying her playful inflection. Rage burned behind her bloodshot eyes. "You men are all the same... FUCKING ANIMALS!"

As Yui finished her sentence, she tightened her grip and started to crush the man's throat, but not so hard as to kill him instantly. In a fit of rage, she used all of her demonic strength and pulled the man's head off.

The man's screams died out instantly. Blood splattered everywhere as Yui ripped off the man's skull pulling out his spinal cord. The blood from the man's body began to flow out like a fountain as she kicked the torso away with so much force that it cracked the wall in front of her. The body fell over into a mushy mess, as all the bones were shattered.

Minutes passed as Yui breathed heavily, looking around at her work. All the blood would make anyone faint from the horror.

"Ehehe~" she chuckled, using her free bloodied hand as she painted her face. "Just another day of work... It never gets old."

As she smiled at the mess she made, she felt slightly disappointed. Her fit of rage didn't let her cut her victim's head off perfectly.

"Shit, his spine came out." She frowned as she grabbed the spine from the man's head and carefully detached it, smiling in satisfaction. "Perfect!"

She couldn't leave such a mess behind, someone would eventually find out, so she extended her arm.

All the blood throughout the alley seemed to levitate slowly towards Yui, as if by some strange force. As the blood seeped into her skin, her appearance regressed from the bloody red into the pristine state she had maintained before.

With this method, she managed to cover her tracks for nearly two months.

"Another one to the body count," she said, playing around with the decapitated head as if she was playing with a ball, still chuckling. "I can't wait to get my place in the ranks of the Twelve Demon Moons. I can get more praise from that man once I reach my goal..."

She was certain that she would get it. Any Demon that would attempt her strategy was bound to get attention from the Demon Slayer Corps, and they would easily get tracked by them, but with Yui's ability, that wasn't an issue.

The Demon Slayer Corps. An organization of fools who dare to oppose the demon race. They were weak and frail compared to the superiority of demons. If Yui ever found one of them, she would take her sweet time before killing them.

"Well then, it's time to take him back to where he belongs," Yui said, referring to the head resting on her hand. She ripped some cloth off her kimono and wrapped it around her victim's head. She always did this to them out of the public eye and it had worked ever since she started. It was now a hobby to her.

However, just before she was about to leave the alley, she felt a chill down her spine. Her demonic instincts were screaming at her to move. Wasting no time, she leaped forward and turned around only to see a shadow coming to her at such speed that she barely had time to react. In the nick of time, she jumped and used her demonic strength to dig her nails into the wall.

She winced as she felt a sting in her neck and dropped the head she was carrying. She flinched as she touched the part that hurt. Pain, it was an unmistakable, yet foreign feeling she had long forgotten. The cut on her neck wasn't deep, it was shallow, but it was regenerating at a slow rate and that worried her.

From the high ground, she glared at her attacker. It was a man—no, a brat. He had short snowy hair with blue strands and wore a pair of small glasses over his icy blue eyes. Over his average-build body, he wore a navy blue yukata as his only choice of clothing.

Yui would have mistaken the brat as a normal human citizen if it wasn't for the katana he was carrying. She knew a Nichirin Sword when she saw one. It was a beautiful sight to behold though. The sword was of a bright sky blue color that shone through the night, with white bits engraved on the blade. The blade also had a curved hilt in the form of a snowflake, which combined perfectly with the weapon's design.

Yui would have stopped to compliment the boy on the design of the blade if she wasn't so unbelievably furious with him. How dare a pathetic worm like him damage her? Yui could feel the veins bulging from her neck, her blood lust rising immensely. The kid turned to look at her dead in the eye, his emotionless face only making him even more fearsome.

"I missed."

Yui's eye twitched. Did this kid have the annoying habit of stating the obvious? Or was it just a weak attempt to provoke her? Either way, she wouldn't let this brat get to her that easy. If he really was a Demon Slayer, then she needed to incapacitate him first so she could torture him later.

"You will regret that, brat. I can't wait to have tons of fun with you~" Yui said coyly, before she let out a bloodlust-filled grin and leaped downward to her target. She was so fast that it surprised the kid, prompting him to dive forward, barely managing to evade a fatal blow to his spinal cord. Still, the damage was already done: the demoness managed to scratch his skin which was all that she needed.

She extended her arm.

"Blood Demon Art: Vampirism!"

After Yui shouted those words, the blood from the kid's wound started to levitate towards her, slowly sucking the life out of him. The kid fell to his knees as he seemed to slowly lose his strength.

"Ahaha! What do you think of my ability, it's good isn't it~?" Yui cackled, her face red from the complete ecstasy she was feeling from sucking the blood. It was not Marechi, but it was still blood of high quality. Yui then got closer to her immobilized target, enjoying every moment she got to taste his blood. "Not bad, you will certainly satisfy my appetite for at least three days with your blood."

Still, Yui stopped as she saw that the kid was standing up, seemingly unaware that his blood was being fed to her. What came next surprised her: the kid started to slowly breathe, taking a combat stance and staring at her with no emotion present on his face.

"Ice breathing, First Form: Freezing Lunge."

The kid lunged at her like a bullet. She was taken aback by the brat's sudden change of speed, but she was prepared this time.

She dodged the obvious attempt to strike her neck, but the brat wasn't done and he recovered fast. Once again, he charged, this time with a different position.

Yui dodged one strike.

Two strikes.

Eight strikes.

Sooner or later she was going to get slashed and she knew this. Startled, she climbed the walls with her nails, where the kid couldn't lay a finger on her. He was strong, but Yui wasn't going to admit that. A human worm like him didn't deserve a single bit of praise from her, even worse if he was part of the Demon Slayer Corps. The fact that this kid even had a chance against her pissed her off to no end.

Screw the torture, she was going to end him now.

"Damn insect, I'm going to suck every last drop of blood out of your worthless body!" she snarled, reactivating her Blood Demon Art causing the blood of the wound on the kid's back to fly towards Yui's skin. She hated that she wasn't strong enough to rip him apart in close quarters, so she chose the safer option to stall him until he bled out.

"You're strong," the brat said, taking back his battle stance. When Yui saw this, she understood now why she was so startled.

She felt it.

She felt the cold, calculating anger on each swing.

Sweating, she tried to augment the effects of her powers to incapacitate the brat faster. How was he not out of commission yet? She already drank two liters of blood out of him, any normal human would at least be dizzy at this point.

The kid started to breathe again.

"Ice breathing, Fourth Form: Ice path."

Yui saw him; the brat was getting closer towards her, but how? She was ten meters up in the air, there is no way a kid like him could reach her. She would have noticed if her target moved from her spot.

Her eyes widened— the worm was wall climbing! He was sliding the coarse walls as if they were full of grease. The movement was fast, fluid, and unyielding.

Panicking, she kicked bricks from the building to throw them towards her attacker. "Get away from me!" she shrieked to deaf ears. The kid kept coming like an unstoppable force. Nothing fazed him, he had his eyes set on her alone. Yui wanted to scream, move, or even try to find a way to attack him, but she was too scared to move. This was the first time she ever felt vulnerable after becoming a demon.

It all happened at a bullet's pace.

The cold steel passing through her neck, her vision getting blurry as she fell to the floor. Her headless body falling beside her, and the kid gracefully jumping down beside her. She couldn't move, everything felt numb.

'Is this it?' she thought as her body started to crumble away. The kid sheathing his blade back and making his way towards the head she was carrying earlier. Not like she cared at this point, but what was he doing?

The kid lit a match.

'Ah, so that's it.'

It was some kind of act of honor. If you don't know someone's name, then the best way to honor them is to burn what's left of them. It was a sad way to go, but at least it showed that the brat—no, the man—had some self-awareness of his surroundings and wasn't some mindless killing machine.

Unlike her.

Well, at least she would finally die after the burning sensation was over.

'I'm sorry Lord Muzan, I failed you…'

She finally closed her eyes, as the final parts of her body crumbled away to dust.

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The times that Tanjiro Kamado felt overwhelmed were a lot, but nothing could be compared to what was happening now.

After defeating The Swamp Demon, he was tasked with another mission right away—as if his first mission wasn't exhausting enough. He was tasked with going to the big city of Tokyo, all the way into one of its most crowded districts, Asakusa. Being a boy who lived in the mountains for all of his life, Tanjiro didn't take too kindly to the atmosphere of the city. He felt dizzy just standing by the crowd of people.

His sister, Nezuko Kamado, probably shared the same feeling as him, as she was on the verge of falling face-first to the ground. While Nezuko was a demon, she was a special case that didn't need to consume humans in order to survive, much to Tanjiro's relief. However, that meant that Nezuko had to sleep at almost every moment to control her demonic urges. Because of this, it surprised Tanjiro that his sister wanted to be outside of her box.

On his way to Asakusa, Nezuko kept scratching the inside of the box a couple of times, urging him to get her out. She probably was excited to see a new place like the city, and that was a rare case considering that she rarely got out of her sun-protecting box. So Tanjiro complied and let her out, which was why he felt instant regret once they foot into Tokyo.

Tanjiro was trying to process why the city was so active at night. Most of the people that live in villages go back to their homes once the evening ends. They want to rest from a hard day of work, so the streets are dark, eerie, and abandoned. In Asakusa, things were different: the streets were full of life and activity, which was why he felt out of place being there.

Most of the time, he would focus on the job at hand, which was finding the notorious "Ghost Demon" that resided in the city.

That could wait. He needed some food now, fast.

"Let's go, Nezuko," Tanjiro said, gently pulling his sister away from the crowd.

On his way to the district, he spotted a food cart that didn't have that many people in it. Backtracking a bit, he spotted it, a wooden food cart under a lampost. The stand itself contained simple decorations like food pamphlets with a very limited menu of food: udon, soba, and ramen.

As Tanjiro approached the cart, he could see that it was run by a man—no, a teenager no more than 15 years old. He had snow-white hair with blue strands, icy blue eyes that were covered by a pair of half-rim glasses. As soon as he got close to the stand, he could see that the boy tensed a bit, narrowing his eyes as he studied both Tanjiro and Nezuko.

He was fixing his gaze particularly at the katana he was carrying.

Oh no, he forgot! The Demon Slayer Corps weren't recognized by the government, so nobody should know of its existence. That means that he was illegally carrying a katana in a public place, jeopardizing his mission.

"A-ah, don't mind this, I'll just put it away slowly…" Tanjiro stuttered, nervously putting the sword on his back—as if that mattered at this point.

"Hot or cold?"

That confused Tanjiro a bit as he'd barely regained his composure when he heard the boy speak, so he let out a surprised "What?"

"Your udon, do you want it hot or cold?" the boy repeated, with no hint of emotion present in his voice. He was briefly glaring at Nezuko, but quickly returned his gaze to Tanjiro, something that he took notice of.

"Oh, cold, with yam topping, please." Tanjiro smiled, the dizziness coming back as he started to feel the weight of the city once again.

The boy nodded and started to work on the noodles. Tanjiro took a seat on a nearby bench and started to recover his energy while waiting for his food. Who would have thought that it was a good idea to send a mountain boy to a crowded city? The Demon Slayers sure had a hard line of work when it came to slaying demons. They must be prepared to go to all kinds of places to slay all kinds of evil demons.

Not like Tanjiro wanted to complain anyway, he was prepared to slay the demons that deserve it. His path would eventually lead to Muzan, and by then, he hoped that he would be more than ready.

That didn't matter now, he was here to focus on other matters, mainly concerning the "Ghost Demon" that resided here in Asakusa. His crow didn't give him much detail, just that this demon had been lurking around in the district for at least 2 months feeding itself with the population. That enough made Tanjiro determined to track down this demon and put an end to its frenzy before it killed more innocent people.

Tanjiro came back to his senses as he heard the sound of a sword unsheathing behind his back. He turned around and gawked as he saw that the udon boy was working skillfully on his dish, but that wasn't what surprised him the most. He was cutting the dough with a huge sky blue knife that looked like a katana.

No wait, it was a katana! A nichirin one to boot.

Ignoring the fact of how weird it was to cut food with a combat weapon, Tanjiro now had a wave of questions to ask the boy. Why does he have a nichirin sword? Is he a slayer? Does he know that Nezuko is a demon by the way he was briefly frowning when he looked at her? He had to ask the most important question first.

"Isn't it illegal to carry a weapon in a public place?" Tanjiro asked, curious about his choice of cooking tool.

"Clearance," the boy said, not even sparing him a glance.

A small but audible "Oh" escaped from Tanjiro's mouth as he didn't dare to say anything else and went back to the bench. There, he just kept staring at the boy and watched him work.

'He smells as if he has encountered a demon recently…' Tanjiro thought as he focused on his acute sense of smell. He knew the smell of demon blood when it came up, it was unmistakable.

The boy himself wasn't a demon, he smelled and looked human, so him being the culprit was out of the question. That didn't mean that he wasn't involved with the demon. Tanjirou got up from his bench and approached the boy, who was currently focused on his work.

"Hey, could I have a minute of your time please?"

No response. The boy kept focused on his work as if he wasn't acknowledging his presence.

"Hey, did you hear me?" Tanjiro asked again, this time raising his voice a little higher. "I asked if I could talk to you for a second."

"I'm hearing you," the boy uttered monotonically, still not looking at Tanjiro.

He was getting slightly irritated. It was rude not to look at someone when they were talking to you. He didn't mind that much though, as he just needed to ask a simple question.

"Do you know something about the 'Ghost Demon'?"

The boy briefly glanced at Tanjiro before getting back on the noodles. "Yeah, I killed her."

Tanjiro blinked once. Then twice.

"Y-you killed her?!" Tanjiro gawked as he caught up with what the boy meant, eliciting a nod from the other.

He was surprised that a boy of his age managed to kill a demon. He was dressed like any normal civilian and he didn't even have the corps uniform on him. Of course, there was a possibility that he might have a spare back at his place—the nichirin sword he had only backed up Tanjiro's theory.

"Here is your udon. That will be 200 yen." Tanjiro was brought out of his trance as he was handed the neatly decorated bowl. The noodles had the yam toppings he asked for, which were neatly cut. And it took no time at all. He wondered how much experience the boy had.

"Thank you." He grinned, grabbing the bowl with no hesitation, leaving the money on the counter. "Hey, what you said to me just added more questions. How did you manage to kill the demon? Are you a slayer from the corps?"

The boy frowned at the mention of the corps. The smell he emitted went from neutral to angry really quickly. "I have no reason to answer anything. Especially to someone who travels with a demon."

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This time, Tanjiro's face twisted into a scowl. "She's my sister and she hasn't killed a human in her time as a demon."

The boy sighed. "I don't know about that, but since she hasn't caused trouble here, she's not my problem," he said in a dismissive tone, then pulled out a rag and started to clean his counter. "Finish up, and then get out of Asakusa. You have no business here anymore."

"You should at least send a crow and report it to the corps," Tanjiro said, his face showing worry. "That way you can let them know that you have taken care of the problems here."

"I don't care about the corps!" The boy raised his voice as Tanjiro recoiled back at the sudden change. "I'm not a slayer nor do I want to have anything to do with them. I'm just a normal citizen who happens to keep the city clean of demons. Got it?"

"That's far from normal though…" Tanjiro mused, trying to defuse the situation.

"Don't try to get smart with me," the boy hissed before taking a deep breath, seemingly calming himself down. "Listen. You seem nice and all, but I really don't want to do anything with the corps. Just finish your bowl, take your demon sister, and don't bother me anymore."

"I… alright then," Tanjiro muttered, looking like a deflated balloon.

"Good. If you'll excuse me, I have to keep working," the boy said, then pointed towards the counter. "You can leave the bowl there once you're finished, I'll take care of the rest."

Tanjiro nodded as the boy went back to work. He was sad that this boy didn't use his strength to help the corps. Even if Tanjiro hadn't watched him fight, he could tell by the smell that this boy was strong. His sense of smell let him tell what kind of person he was dealing with, but it didn't let him tell what happened in said person's past.

Whatever this boy might've gone through in the past, it must have been something horrible that he didn't trust even the Demon Slayer Corps.

Are the corps that bad? No, that cannot be the case. Tanjiro hadn't met with anyone of the corps yet, but if they had someone as kind and caring as Urokodaki, then he could definitely trust them. It must be some kind of personal problem this boy had with them.

Tanjiro let out a frustrated sigh, sitting on the bench beside his sister, who was now sleeping.

"So she can sleep while sitting down…" he muttered to himself while staring at her. He didn't know that Nezuko had this habit back when they were living with their family, they always slept on the floor. Then again, Nezuko had been acting weird ever since she became a demon, so it was no surprise to him.

As Tanjiro was about to gobble up his udon bowl, he smelled something awful that froze him on the spot. The smell was so repulsive, yet very familiar, that he dropped the bowl to the floor. Without noticing the mess he made, he stood up, sweating profusely as he tried to track the source of the smell. It was back in the main district.

He couldn't forget whose smell this was. It was him. Muzan Kibutsuji, the man who killed his family.

"Hey, you broke my bowl…"

He could hear the boy hissing behind him, but Tanjiro paid him no heed. Baring his teeth, he stood up and stormed out as fast as he could.

He could not let Muzan escape this time. Not after all the innocent lives he took.

He. Will. Be. Put. Down.

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"Okay Kazuki, pull yourself together. It's just a stroke of bad luck, nothing more."

Kazuki rubbed his temples as he watched the slayer run away after breaking his bowl. He could chase after him and maybe catch up to him, but that would probably not be a good idea. Kazuki had a normal yukata, while the slayers had clothes that allowed them specifically to move freely in combat.

Still, Kazuki was pissed. A Demon Slayer comes and asks questions that are very uncomfortable for him to even answer, then he decides to order a bowl of udon, doesn't even eat it, and drops it to the floor without reason. All of that and Kazuki only got merely 200 yen, and considering how much that bowl was worth, it was more of a loss rather than a benefit.

What bugged Kazuki the most was how desperate the slayer seemed when he stormed off. It was like a kid throwing a tantrum because his mom didn't get him what he wanted. He even left his sister and a weird box behind.

'Should I kill her?'

Those were Kazuki's first thoughts as he watched the sleeping demon. His job was to keep every threat away from Asakusa, so everyone could live peacefully. This girl was acting off: no demon could be harmless for an extended period of time, most of them went berserk after the moment they transformed. There were special cases though, and he knew a certain pair of harmless demons, but outside of them, every demon he met was crazy for human flesh.

Kazuki could slice her head off and avoid a possible threat that might harm people in the future—that way, many would be safe. Or he could wait until that slayer came back and took her away to who knows where, risking the lives of many people wherever this demon went.

She was the sister of that slayer, if he went on his way and killed her, then he would have to face his anger, and it was not a good idea to fight a trained slayer. Not like he wasn't trained himself, but it would be too much trouble to handle.

'Still, she seems… harmless. Way too harmless,' Kazuki thought. Maybe this is something that can catch that person's interest, it could be that this is what she sought all this time.

It was too risky. This girl could be a threat to her for all Kazuki knew, and she may not be the one demon she needed. He might have been thinking about this too hard, but he was quite the salesman. After all, he managed to maintain his udon stand for three years, ever since he was 12 years old.

'I-Is it really the right thing to do? Kill her?' Kazuki thought, uncertain of what he should do. If this demon was alone, with no company at all, then he wouldn't hesitate to take her down. He wasn't uncertain because he was scared of her older brother.

It was because they were siblings.

Sibling bonds were a thing that Kazuki hated, an old wound that he had on his soul, something that wouldn't heal easily. However, as much as he hated them, bonds were not something Kazuki wished to destroy, and if they were genuine, the more reason to keep them. He had no way of knowing how strong the bonds were with this family, but he could ask the slayer once he returned.

Should he take that gamble? Letting the girl live?

The superior men understand what it's right, the inferior men understand what will sell.

This is what he believed was right. He would let her live, for the moment.

He exhaled harshly, calming himself down as he felt the stress go out from his body. He then turned to the demoness, who was now awake and staring at him with a neutral expression, the muzzle making it hard for Kazuki to see what face she was making.

Well, better do it now that she's awake.

He went to the stand and took his katana that he always carried with him. His trusted weapon that he used to kill demons and after very careful cleaning, to cook. Weird as it may be, it worked for him ten times better than a regular knife.

Kazuki went closer to the demon girl, glaring down as he was inspecting her every move. The fact that the girl had no reaction after seeing his sword unsettled him. Any normal demon would have launched at him or done some strange trick with their abilities. This wasn't the case.

"So…" Kazuki started, fixing his glasses. "Demon girl, can you understand me?"

She tilted her head and nodded. That was progress, if she could understand basic human language then he wouldn't have to waste drawing or using body language.

"Good, I have some questions for you. Hope you can answer them, your life depends on it after all," he said, ignoring the girl's widened eyes. "Have you killed any humans in your time as a demon?"

The girl shook her head.

"Hmm… why should I believe you?" Kazuki squinted, trying to see something, anything of the girl's movements to see the truth.

"Mmph. Mmph!"

Kazuki slowly nodded at the girl's gruntings. "Great, I got nothing out of that," he said, making the girl deflate.

"So, limited vocabulary, this could be a problem…" Kazuki mused to himself as he started to gather his thoughts. If the demon girl couldn't speak, then it could be hard to tell if she was lying or not. After all, the tone someone gives when they're talking is the biggest lie detector.

He sighed. Things had become harder for him now, but they all had a solution. He turned to address the girl once again.

"Listen, I can't ignore your brother now because he broke one of my bowls. And those aren't cheap. I can't also say that I believe you because I can't understand anything you say, so I cannot be sure if you're lying or not," he said, making the girl moan in sadness. The girl would be pouting if it wasn't for that muzzle.

Kazuki was taken aback by the girl's attitude. Every action she took, every sound she made, it all felt completely human. Yet her appearance marked her as a demon, her unnaturally shaped eyes and her very long nails are a giveaway.

She was an enigma.

'Maybe Tamayo-san knows what's going on.'

As Kazuki tried to rack his brains to solve this demon's behavior, he could see from the corner of his eye that it was a short old lady approaching him. Kazuki knew who she was, Sato Maya, the owner of the flower shop in the main district. She looked very scared, which was unhealthy for someone who was nearly at the age of eighty.

"Sato-san, what brings you here?" Kazuki asked, helping her to sit down beside the demon girl. "You should calm down, it's not healthy for someone of your age to get this alarmed. Stay here, I will make you some tea."

"I… thank you, Kazuki," Maya said, exhaling as she placed a hand on her chest, trying to calm herself down.

Kazuki quickly made his way to make a special herbal tea of buckwheat, a plant that is used to make soba noodles. He had soba ingredients on his stand because people—who were mostly drunk—couldn't read the sign that said 'udon only' on the cart, so they often asked Kazuki to make them soba, which he didn't specialize in.

Still, the more money, the better. He eventually gave in, so soba was branded as a 'secret' where only the ones who asked for it may receive it.

So Kazuki used the buckwheat and started to boil water, making the tea for Maya in little to no time. It would help her to calm down so she could talk without pressure.

As he returned to the bench, Kazuki felt the urge to drop the hot teacup as he watched Maya pet the demon girl like it was her own child. And the girl liked it, her cheekbones rose every time Maya started to tickle her, scratch her head, and play with her cheeks.

'Another thing to add, this demon girl has the mind of a child…'

Kazuki found himself staring for a good two minutes at how the scene was unfolding. It was only a matter of time until the old lady noticed him.

"Kazuki, who is this girl?" Maya asked, grinning as she played with the demon girl.

Kazuki blinked. "Oh. Uh. She's… my friend's little sister." he managed to say, albeit awkwardly. He wasn't used to lying.

"I see… your friend certainly has a cute little sister," Maya said softly.

Kazuki rolled his eyes, handing the cup of tea to the old lady. "Right… here's your tea, Sato-san. It's made from soba, it'll help you calm your nerves."

Maya smiled as she stopped petting the demon girl, much to her dismay. She then took the teacup and started to drink its contents. She gave a soothing smile as she seemed to enter a state of total calmness.

"Feeling better now?" Kazuki asked, careful not to alarm her about whatever happened to her.

"Yes, I'm better, thank you Kazuki. I assume you want to hear what happened to make me that afraid?" she asked, to which Kazuki nodded. "I figured. Well… I was going to close the shop for the day as usual. Everything seemed crowded and normal, until…"

Kazuki placed a reassuring hand on her shoulder as soon as he heard her voice becoming shaky, making the woman relax.

"Then I saw a woman getting attacked out of nowhere. T-The man was literally trying to eat her alive!"

Kazuki's eyes widened. This was obviously the work of a demon, no man would ever think of eating someone out of the blue. Still, all this didn't add up. If this demon was eating people in the main district, then he would've heard the news sooner.

"Trying? What do you mean by that?" Kazuki inquired, this time a little more impatient than before.

"W-Well, luckily a young kid of approximately your age stepped in and subdued the man. The woman got slightly hurt, but no one was killed thanks to him… I don't really know what happened next, the boy then disappeared out of thin air alongside the couple," Maya explained as her whole body trembled. "T-They were a married couple, Kazuki… I don't know why all of a sudden the husband decided to try and eat her! What caused him to try that?"

"Something inhuman…" Kazuki muttered, earning him a confused look from the old lady. It was a normal thing for demons to attack humans, but to go from normal to insane in a span of seconds? That was another story.

That could mean that the man was turned into a demon at that exact same moment… and there were only a few demons capable of that vicious transformation.

'This is bad news. There is also the fact that no human is able to just disappear into thin air, so what Sato-san saw at the end was most likely an illusion. Looks like Tamayo-san was there when it happened.'

Kazuki's eyes widened, anger coursed through his body as he started to put the pieces together. 'The only possible explanation for this vicious transformation can be via an Upper Moon demon, or… Muzan Kibutsuji.'

He took a deep breath as he let the information sink in. No one, not even the Pillars were ready to face an Upper Moon Demon, not least the progenitor of all demons himself.

"Kazuki?"

Kazuki broke out of his trance and turned to Maya, who was looking at him in worry.

"Are you alright dear?" Maya asked as she handed him a handkerchief. "You're sweating…"

He took the handkerchief and started to wipe the sweat from his forehead. "I-I'm alright Sato-san. It's just a bad feeling, that's all."

Kazuki quickly took his sheath and bowed to the old lady. "Sorry Sato-san, I have to go now. The tea is free so you don't have to pay for anything."

Maya nodded, seemingly satisfied with Kazuki's concern. "Well… someone as old as me shouldn't be prying into other's business," she said, smiling as she kept drinking the tea. "Take care Kazuki."

Kazuki nodded, walking towards the demon girl who looked at him impassively. "We have to go now. Follow me, I know a doctor who can help you with your… demon problems."

The girl tilted her head, seemingly not understanding what he was saying. Kazuki placed a palm on his face. He forgot that this demon had the mind of a child.

"If your brother was the one that Sato-san mentioned, then I think I know where he will go," he said. What he said wasn't a lie, in fact, it was a half-truth. If this girl's brother ran towards the main district because he somehow sensed a threat, then there was a good chance that he was the one who stepped in.

The girl beamed, standing up as she started to follow him.

Kazuki sighed, knowing that he'd got involved in something that he thought wasn't his problem. He really had the worst luck.

----------------------------------------

"Nezuko, Nezuko?!" Tanjiro shouted, scouting every corner of the area for his sister.

After his unpleasant encounter with Muzan, Tanjiro ran to fetch his sister in order to get help from the demon lady who had helped him contain the unfortunate soul of a man that got turned. She said that she could help him regarding the problem with Nezuko, and he didn't want to waste an amazing opportunity.

When he didn't find her sleeping on the bench as she should have been, he started to panic. Even the box he used to carry her was empty. The udon boy wasn't here either.

He could discard the option that the boy kidnapped her. He didn't have that type of smell when he first met him. Or maybe he did take her somewhere, but without ill intent.

"Hey…"

Tanjiro turned to the voice that addressed him and blinked at the sight in front of him. A boy with pale green and black hair, with lavender-colored eyes. He was one of the pair of demons that he encountered when he had his incident in the main district.

He could trust him.

"Come with me, your sister is already with Tamayo-sama," he said, frowning deeply as he looked at Tanjiro. "Stop looking so desperate, or you'll make her worry about something so petty."

Tanjiro perked up at the mention of Nezuko. "Wait, she's already with her?" he shouted, running towards the demon boy in an attempt to shake him. "Please tell me where!"

"Don't touch me with your filthy hands!" the boy yelled, chopping Tanjiro in the chest, stopping him in his tracks. "Kazuki took your sister to Tamayo-sama to save some time. Do you understand that? Good. Let's go."

Tanjiro didn't know if the boy was unaware that he almost killed him with that chop. It left him wheezing for air for a good 30 seconds before resuming his walk. That left him with a reminder that he was dealing with an actual demon and not a boy on the streets.

As they walked towards an alley in a remote place, Tanjiro finally caught up with what the demon boy said earlier.

"Who's Kazuki?" Tanjiro asked, "I didn't meet anyone with that name before."

"Seriously?!" the boy snarled, not turning to look at him. "From what he told me, you already met him. Short stature, white hair with blue strands, disgustingly ugly, and wears glasses."

Tanjiro blinked as he heard the ugly part until the description started to match a certain boy he met earlier. "Oh, the udon boy? So his name is Kazuki?"

He nodded. "That's right. That stuck-up brat…" Tanjiro let out an awkward smile as he smelled the clear anger from the demon boy. "Anyway, we're here."

Tanjiro gasped as he saw that they were standing in front of a wall, a plain one at that. If this is the place they were going to go? It was located in a remote area, away from the district; it made sense, a place well hidden from any demons and humans who could try to locate them.

Surprisingly, the demon boy just walked forward, which should have resulted in him crashing into the wall but to Tanjiro's surprise, he just phased through it.

Tanjiro gawked as he witnessed something out of a fairy tale. Then again, he just recently faced a demon who could swim on land, so he wasn't that shocked when he remembered the demon's abilities.

He walked forward and phased through the wall. Tanjiro's eyes widened as he saw a fairly big two-story house. It was plain looking, as it had almost no decorations on the outside, only a weird paper talisman stuck on top of the door. It made sense, they didn't want something so notable in their house.

As Tanjiro and the demon boy made their way inside, they immediately entered one of the rooms. Inside, Tanjiro was more than relieved. Nezuko was rolling on the ground on her own, bored out of her mind, until she perked up and ran towards her brother.

"Nezuko!" Tanjiro grinned, dropping whatever worry he had as he went to hug his sister. "Thank god I finally found you, I was worried…"

Nezuko squealed, happily hugging his brother back. As Tanjiro turned to look around the room, he jumped as he found himself being stared at by three people. The pair of demons, and the boy he met earlier, Kazuki.

Realizing his mistake, Tanjiro quickly bowed. "I- I'm very sorry for entering so abruptly!"

The woman merely gave him a sweet smile. "That's quite alright, it really shows how much you care for your sister."

Tanjiro smiled back, although it quickly disappeared as he felt the killer intent from the demon boy.

Someone has a very short temper…

He then turned to Kazuki, who was too busy speaking with Tamayo. Tanjiro remembered what Kazuki had done and quickly made his way towards him. As soon as he got close to him, Kazuki frowned which made Tanjiro recoil back a bit. Still, it took more than that to intimidate him!

"Thank you for bringing Nezuko here," Tanjiro said, smiling as he bowed in gratitude. "I was worried that something might have happened to her."

Kazuki narrowed his eyes. "You still owe me 2000 yen for that plate you broke," he said, "and please, don't bow, it feels weird."

Tanjiro resisted the urge to scream. 2000 yen? That was absurd! "2000 yen, that much?!"

"In reality, that bowl was worth 1800 yen." Kazuki scowled, crossing his arms. "But the fact that you didn't eat my udon pissed me off."

"I'm so sorry, here is the money!" Tanjiro bowed apologetically, pulling out the spare money Urokodaki had given him.

"Kazuki…" He heard the lady's tone shift into a more harsh one. "What did I tell you about charging people unfairly?"

That caused Kazuki to shiver in fear as he lowered his head a bit. Tanjiro could swear he saw his face going beet red from embarrassment. "I-I guess I can only charge you a fair amount," Kazuki stammered, taking the money from Tanjiro's hand. He left some coins there. "...So I'll take 1800 yen for it."

"See what you did?!" the demon boy shouted his displeasure. "You made Tamayo-sama mad!"

"Yushiro, you upset her on a daily basis by harassing anyone that comes even slightly close to her," Kazuki deadpanned as his blue eyes bore through the demon boy in anger.

"What was that?!"

"Stop it. Both of you," Tamayo ordered, causing both of the boys to squeak. It was like watching the leader of a wolf pack calming down a bunch of troublesome cubs.

"Yes…"

'Not gonna lie, they're like a pretty unstable family…' Tanjiro thought, making an awkward smile as he didn't know how to respond to the situation.

Tamayo sighed. "Sorry about that, both of them can be a bit noisy sometimes," she said, glaring daggers at both of the boys. "This is not how I wanted introductions to be going."

Their shoulders slumped. "We apologize…"

"As you already know, my name is Tamayo. I'm a doctor. These boys are Kazuki and Yushiro respectively. Boys, this is Kamado Tanjiro." Tamayo shook her head in disapproval, then turned to look at Tanjiro. "Please, let us go into a more suitable place."

Tanjiro nodded as they all went to the living room. On their way, Tanjiro saw the woman that was attacked earlier by her husband, who luckily didn't sustain any serious injury, but it may leave her with a deep emotional scar. The poor soul.

So they were sitting in the living room, and Tanjiro could tell that things were different between Kazuki and Yushiro. They had no hate for each other regarding their stupid argument earlier, so it could safely be said that their bickering was a normal thing around here.

"Kamado," Kazuki started, arms crossed. "I want you to tell me the truth regarding this subject. Don't lie."

Tanjiro nodded slowly, unsure where this was going.

"The demon you saw in the main district. Was it an Upper Moon or Muzan Kibutsuji?"

Tanjiro blinked. Upper Moon? What was that, a special type of demon that was different from the ones he had fought?

"Upper Moons? What are those?" Tanjiro asked, curious and intrigued.

"They haven't told you about them?" Kazuki asked, only for Tanjiro to shake his head. "Strange, that's basic knowledge for every slayer. Very well, we will explain to you everything about them."

And so, Tanjiro spent the next 10 minutes learning about the existence of the Twelve Demon Moons. They were the strongest demons in existence, excluding the progenitor of demons himself. They were divided into two sections: Upper Ranks and Lower Ranks. These were divided into six ranks, from weakest to strongest.

Slaying a Lower Rank Moon was pretty much a requirement to join the Pillars, so Tanjiro assumed that they were very strong. Still, they were manageable for the corps, as the pillars could take care of them.

On the other hand, The Upper Moons were another story. Tamayo and Kazuki didn't have much information on them because no one had lived to tell the tale. They were so strong that they had managed to slay a lot of Pillars through the ages.

Those tiny details made Tanjiro quiver, it would take a great deal of training and experience to even rival their strength. That didn't mean he could not defeat them.

"I see." Tanjiro gulped, shocked by this new information. "The demon I saw in the district...was Muzan Kibutsuji."

The silence in the room was suffocating for him. No one said a single word as they were trying to process the information. Kazuki closed his eyes, as he clenched his yukata tightly. Yushiro was scowling deeply. Tamayo was apparently the calmest one, but Tanjiro could smell the anger from her when he mentioned that name.

It made him wonder how much she suffered when she met Muzan.

"I see…" Kazuki was the first to break the silence. "That's certainly a problem, but an Upper Moon could have been worse."

"Because Muzan moves on throughout multiple places?" Tanjiro asked, trying to follow his lead.

Kazuki nodded. "Exactly. Muzan is not prone to stay in one place where the corps could easily find him. It is how he has stayed hidden for years," he explained. "Upper Moons can settle in one place if they want to, luring slayers and civilians. Sure, Muzan kills a lot of people, but he's not as chaotic as his servants. Muzan's long gone from here."

"That makes sense," Tanjiro said, feeling frustrated for not being able to do more when he encountered him.

"In any case," Tamayo spoke up, gaining the attention of both boys. "It's time to tell you why we are so different from the normal demons you have encountered."

Tamayo started to explain every single detail about the alterations of her body, how she turned Yushiro into a demon, and Muzan's curse. She talked about why she needed blood to survive despite her alterations, and how Yushiro needed less blood than her.

Tanjiro understood and was amazed by how Tamayo could suppress her urges for devouring humans. She had been doing this for more than 200 years. Not only that, she was a medic, so that meant that she saved people from death.

Ironic, a demon saving people from death instead of bringing it to them. It's almost a miracle.

Regardless, Tamayo was someone that he could safely trust.

So Tanjiro asked the crucial question. Can he turn his sister back into a human?

"Yes, there is a way to turn her back to a human," Tamayo said, giving him a look of worry. "But it's not going to be easy…"

"And we're not helping him."

Everyone, including Tamayo, turned to look at Kazuki, who spoke his clear displeasure on the situation. Tanjiro felt his blood boil as he heard what Kazuki said. He was very close to turning Nezuko back to human, so why didn't Kazuki want to help?

Tamayo remained silent. She looked saddened about something, but Tanjiro couldn't picture what.

"Kazuki, are you questioning Tamayo-sama's decision?" Yushiro hissed as he stood up. "You're not the one to make the decisions for her!"

"As far as I'm concerned, this is also my decision!" Kazuki argued back, standing at the same eye level as Yushiro. "You know that I want nothing to do with Demon Slayers. The pain I- we went through because of them is not something I can forgive."

This time, Yushiro remained silent. For the short time that Tanjiro had known the demon boy, he'd been prone to take Tamayo's side no matter what, and he was always up with some argument in her favor. To see him fall silent meant that Kazuki was somehow right.

"Kazuki," Tamayo spoke up, "you noticed it too, right? Nezuko's behavior is very different from any demons created by Muzan. She could be the one to put an end to all this and finally make a cure to end all this. I'm sorry, but we have to do this."

Kazuki scowled as he turned to glare at Tanjiro, the latter instinctively taking his sister's hand. The anger and sadness the boy was leaking were too much for him to handle that his instincts shouted at him to protect Nezuko.

Kazuki's face softened as his whole body trembled. It seemed like he managed to calm himself down, somehow.

"I- I have to go get some fresh air." With that, Kazuki stormed out of the room, leaving a confused Tanjiro behind. Tamayo could only sigh and Yushiro went back to sit down, not saying a single word.

"Why is he like that?" Tanjiro finally spoke, still uneasy about it.

"It is not my place to say," Tamayo sighed, making Tanjiro deflate. "Kazuki has a long story before he came to me. When he said that he didn't want to work with the Demon Slayers, he was serious about it. Also…" Tamayo turned to look at Nezuko, who was playing with her toes the entire time. "It seems like seeing the sibling bonds between you two has triggered some painful memories from him."

"Is he going to be okay?" Tanjiro asked, glancing towards the window, which showed an unmoving Kazuki in a meditation pose.

"Yes, he's stronger than he looks, and he has a big heart," Tamayo said, letting out a sad smile. "He may not show it, but he's a kind person on the inside, even if he himself doesn't know it."

----------------------------------------

Kazuki sat there, unsure about what to do in this situation. In these types of situations, he would always try to meditate to forget about past problems.

He was supposed to live his life without useless hauntings, so why were slayers getting in the way? They kept pestering him over and over, never leaving him alone. He sighed. He envied those people who could live their lives like normal and were oblivious to the supernatural.

If only his brother… stayed normal.

He shook his head. No, those moments were already lost within the blizzard.

He would try to focus on the matter at hand, which was to help Tanjiro, for the moment. If Tamayo wanted to revert Nezuko back to her human self, then Kazuki would do anything in his power and knowledge to help. He owed her that much.

It was almost funny. Sibling bonds were something that always made Kazuki angry. However, while he hated how strong the bond between Tanjiro and Nezuko was, he didn't want it to break. It was an odd feeling.

"Oh, look what we have here."

Not wasting time being surprised, Kazuki quickly reacted as he got in his combat stance in the blink of an eye. Meditation did help with his concentration.

His instincts did not lie. As he opened his eyes, he could see that there were two figures standing in front of him. One was a young man whose most notable trait was that his eyes were embedded in each of his hands. He also had arrow-like pupils—probably related to his ability. The other one was a young girl with cat-like pupils and unnaturally bright hazel eyes. She seemed to be playing with a temari ball like a child, with a sickening smile on her face.

No hard guesses required. Kazuki could easily identify that they were demons.

"He doesn't seem like the guy we're looking for, but he's definitely here, Susamaru," the arrow demon said, in a baritone voice as he seemed to scan the area with his hands. "The boy with the Hanafuda earrings…"

It was not wise to reveal their plans in front of an opponent. Those earrings only belonged to one person who he recently met, Tanjiro Kamado.

He would ask them later. Once he'd cleaved their heads off. Right now, he only had one thing in mind.

Kill. Demons.

"I'll look for our target, you can deal with this nonsense." The arrow demon grinned, disappearing from Kazuki's sight.

"Okie-dokie, Yahaba~!" Susamaru grinned as she seemed to sense Kazuki's killing intent, throwing the temari balls at full force. "LET'S PLAY!"