Warning(s): Violence and some swearing

Kimetsu No Yaiba is not owned by me

it is owned by its author, Koyoharu Gotouge

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Running through the dense forest Masato was barely able to keep up, it had already been about a day from his departure from Osaka, and he was sure if he didn't get another break he was going to faint, but the last time he asked for a break Satow had pretty much made him feel like a frail old man with the way he was talking. Masato was almost a hundred-percent sure that Satow couldn't have been human, there was just no way someone could run this far and fast with little breaks. His thoughts where quickly interrupted by a branch he hadn't noticed while running, tumbling him face first into the dirt.

Satow, hearing Masato's footsteps stop would turn and see him face first in the ground. "If you really want to become a successful demon slayer, you're going to have to get used to running this far and fast. Breaks could result in the loss of people's lives." Satow said darkly, Masato had figured out that while Satow always seemed pretty apathetic about any other topic, he was very serious when it came to human lives which he couldn't blame him, but it would be nice if Satow was this passionate about everything else. "Besides where almost at our destination it's only a few hundred paces away." Satow said in his normal apathetic tone as he looked at Masato with nothing but disappointment.

"You said that almost two-hundred paces back!" Masato yelled, it wasn't like he wasn't used to walking long distances, but that was walking, he was running with all of his might just to keep up and his legs felt like jelly, and even the ground felt like the most comfortable bed in the world, "There's no way I'm going to be able to keep going I need a break, I'm not superhuman unlike you!" Masato yelled at Satow, for what was most likely the thirtieth time today. He really didn't get along with the slayer, they only shared one thing in common and that was they preferred to be alone whenever they could.

"Yeah, yeah whatever you big baby." Satow was about to go on another tangent most likely going to chew him out for firstly talking to his superior, and secondly being unable to keep up with his inhuman speeds, but fortunately Satow's crow who he figured out was named Zenzo, soared above there heads screaming.

"Caw! Caw! Disappearances at nearby Hosumi Village South-West of here! Hotaka Satow is to go immediately! Caw! Caw!" Satow looked pretty annoyed, probably because he wasn't able to chew me out, "Continue going in the direction we where heading, you should see a cabin at the base of a mountain." Without waiting for Masato to reply Satow at a speed Masato couldn't even register dashed in the direction his crow was leading him to.

"Of course he would leave me in a creepy forest." Masato sighed, he felt a little better now that he had given his legs the desperate break they needed, and decided that staying in one spot would make him more of a target, so readying himself, he would lift himself up and would begin walking in the direction Satow had shown him.

Yasuhiro Residency

The sound of wood quickly hitting wood could be heard as two people where currently sparring, a man that appeared to be in his forties, with a rather slim build, and standing at around 5'11 with dark gray hair mixed with some white his eyes having a mix of teal and blue, and a teen with dark maroon hair that faded to a lighter red at the tips, his eyes weren't to unordinary being dark-brown, having a slim but built physique and standing at around 5'4.

"Moriyama you're breathing is becoming erratic." The older man spoke calm and gently, as he quickly disarmed Moriyama, then dropping below and using his bokken would sweep Moriyama's legs causing him to fall on his rear.

Moriyama would lay on the ground, his clothes damp with perspiration, the hot summer sun feeling like a coal to his skin, as he took quick shallow breaths.

The older man would lend his hand to Moriyama as he took it, using it to pull himself up. "You should go take a break, we'll continue training in twenty minutes."

Moriyama simply nodded, grabbing a nearby towel at a nearby table taking it with him as he headed inside.

As the man followed suit he heard a knock on the door, walking over he opened it to be greeted by the sight of a teen with his hair having a couple of twigs sticking out of it.

Outside of Yasuhiro Residency

Masato was in a terrible mood, first he has to run what felt like three marathons, then got left behind in the middle of a creepy forest filled with every insect known to man, and then if that wasn't bad enough while he was traversing the wilderness he slipped and tumbled down a hill, but at least he had successfully made it to this house. At least he thought this was the correct house looking back he really should've asked Satow what the house looked like or who owned it. All he was given was that the owner was a "cultivator" of something called wind breathing. Whatever that was or meant every time he tried to ask Satow would just say the same exact thing, "He'll tell you when you get there." He was happy he was rid of that guy another day and he would've probably lost his mind. He was quickly brought out of his internal ravings by the door sliding open him being greeted by the sight of a older man probably in his forties, with dark gray hair with some noticeable white strands sprinkled in.

"Um... Hello sir, are you the cultivator of wind breathing?" Masato asked warily he prayed to the gods that this man wasn't the same as Satow or else he might try to find other cultivators, even if it took him months to find another one.

"Ah, you must be Masato. My student, Satow, told me he was sending someone who wanted to learn the breath of wind." The man spoke softly, which was a pleasant surprise to Masato he was half expecting this man to simply have a completely uninterested tone.

"Yes, that's me, and may I ask for your name? Satow-san didn't really tell me anything..." Masato said, internally he was happy that this man seemed to be very kind, but he felt awkward really only because he was expecting to be greeted by a man who wasn't going to care what he did or by a man who was so passionate that it was obnoxious.

"That sounds like something Satow would leave out. My name is Yasuhiro Yasuhiro." Yasuhiro responded with a warm smile, as he stepped aside allowing for Masato to enter, as he slid the door shut behind him as he lead him down the hallway. "Currently there is one other student here his name is, Daisuko Moriyama, I'd like for you two to become friends if possible, and I should tell you he is mute so he cannot speak regularly. He usually uses gestures or pen and paper."

Masato wasn't surprised there was another student to be honest he was expecting more than one, but he was surprised that his peer was mute, but he didn't think about to much ultimately he was just here to train and join the demon slayer corps. "I understand I'll take into consideration his muteness." Masato replied.

"Thank you, and here is he room you'll be staying at." Yasuhiro would gesture to a nearby door. Upon sliding it open Masato would be surprised at just how lavish the place was, first thing that surprised him was a proper bed in the far left corner of the room. He had only seen proper beds at the inn he worked at. Looking around he would take in the room, seeing a desk to the right of the bed, and a cabinet at the far right corner of the room. He took a few more seconds to look around the room before turning to his new master "Thank you Yasuhiro-sensei, the room looks amazing. I couldn't have imagined anything like it." Masato said while bowing.

"It's no problem at all, the cabinet has extra clothes for you to wear, but I suggest not bathing yet as training will continue in about thirteen minutes." Koji replied as he closed the sliding door. his footsteps slowly fading as he walked down the hallways.

"So. I guess I'm staying here until I finish getting trained... I wonder how long that will take." Masato thought, he was still pretty much in the dark Satow hadn't explained what exactly wind breathing was, but he had a hunch it was something to do with those movements he did against the demon. His thought where interrupted by a knock on the door, opening it he would see a boy around his age with dark-maroon hair that faded to a lighter shade of red at the tips, and surprisingly his eyes were a rather ordinary dark-brown. "Um hello, you must be Daisuko-senpai." Masato said, while giving a bow to him.

Moriyama would give a nod with a smile, and would take out a notepad and pen beginning to write something down in it before showing it to Masato. "You don't have to be so formal around me. You can just call me Moriyama." Masato read the note before nodding and asking "Alright, Moriyama, did you need to see me about something?" Masato replied, watching as Moriyama wrote again.

"I was just checking in and say hello, after all were gonna be staying here for the time being. I also wanted to maybe help you train." Moriyama smiled while he saw Masato read the writing. "I'd love to train with you, and... I'm kind of embarrassed to admit this but I don't know anything about wind breathing, or about the demon slayer corps." Masato said meekly, luckily for him Moriyama seemed like a nice guy, and was nothing like Satow. Which made him wonder how someone like Satow could develop from such a good environment and kind teacher.

"Well where would you like to start first?" Moriyama wrote, as he waited for Masato to read and think.

"I guess what exactly is wind breathing? I have a suspicion, but I don't really know fully." Masato said as he waited for Moriyama to finish writing which he noticed he seemed to be writing a lot. He hoped it wasn't to complicated for him to understand.

"Wind breathing is one of the main breathing styles used by demon slayers. Firstly breathing styles utilize breathing techniques. Which allow for the user to gain significant boosts in strength, speed, stamina, endurance, durability, etc. The proper term for breathing is total concentration breathing. Now wind breathing is a breathing style that mimics the wind with it's forms." Masato while reading grew more interested in these breathing techniques, and started to imagine himself doing back flips and effortlessly cutting off the heads of demons, and getting incredibly rich in the process. He was taken out of his day dreaming by Moriyama waving his hand in his face which startled him making him jump a bit.

Moriyama noticing this bowed as an apology, and gave him a thumbs up with a questioning look, hoping he understood what he was trying to convey.

"I think I'm starting to get it, thank you, Moriyama." Masato said, as he heard soft footsteps getting closer noticing Yasuhiro behind Moriyama who turned around to greet Yasuhiro with a bow.

"I'm happy to see you two getting along with each other." Yasuhiro began before turning to Masato, "We'll be beginning training now. Please meet us outside at the courtyard." Yasuhiro said as he walked off, Moriyama in tow.

Masato quickly changed into what he assumed to be a training outfit, after changing he looked at the nearby mirror seeing him in a white kimono, with a dark-green hakama. After ensuring everything was fitted properly he would quickly go outside.

Yasuhiro Residency Courtyard

Upon walking outside he would find Yasuhiro and Moriyama waiting for him the former holding a bokken. "Grab a bokken and join us." Yasuhiro spoke softly, gesturing to the sword rack, Masato would grab a bokken and would stand next to Moriyama as he waited for Yasuhiro to instruct them.

"Today you'll both be doing practice swings, simply raise your sword over your head and swing downward, try to keep it as straight as possible, Masato since you're new to this I want to observe Moriyama and copy what he does, I'll go prepare the next set of training." Yasuhiro explained as he walked into a nearby wooden shed.

Not wasting anytime Moriyama would begin to do the practice swings, as Masato watched trying to copy him. As he tried Moriyama looked over, and stopped swinging to help Masato, Masato noticing would let Moriyama fix his posture, and most importantly what hand the sword goes in which he guessed that even if you're left-handed you have to use your right hand.

Upon swinging again Masato would notice how... Wobbly? The sword was, however, he could now exude more power per swing. "I guess I'll have to get used to using my right hand more." he thought as he looked over at Moriyama "He looks like a professional from where I'm standing. I wonder how long has he been here." he would quickly shake his head and would refocus on swinging his sword.

After what he assumes to be a couple of hours judging by where the sun currently was. He noticed Yasuhiro rounding the corner carrying two giant rocks and two baskets "You both can stop swinging now." He spoke ask Masato quickly let his arms fall and rest as he waited for what Yasuhiro was going to have them do next. "You'll be using these baskets to hold these rocks while running up and down the mountain." He said a friendly smile on his face, which to Masato was more disturbing than a evil grin or just apathy, as he went up to the master he would grab a basket and fill the rock into it. As soon as he put on the basket and stood he could feel the rock weighing him down as he looked at the large steep mountain outside of the residency. Before he could think about anything else he noticed Moriyama run up the mountain, he quickly steeled himself and ran up the mountain trying to catch up to him.

Mt. Oshima

It has been around three weeks since this training started, and Masato could already feel the benefits, he hadn't officially started learning total concentration breathing, which did disappoint him, but he felt that his master had a reason for holding off on it, and he wasn't about to argue with someone as knowledge as him, but even the training he had been doing was improving his body it wasn't to crazy but he could tell he was significantly stronger than before, and he had finally moved up to actually sparing with Moriyama instead of just practice swings, and while he wasn't winning against Moriyama anytime soon, he could see that he was able to block more attacks and his reaction time had increased.

Now all he had to figure out was why he and Moriyama was on the mountain, and most alarmingly why Moriyama was looking pretty shaken they hadn't even done anything yet, but just seeing how Moriyama was looking scared him, he quickly looked forward as he heard leaves crunching seeing Yasuhiro come out from the brush.

"It's been three weeks since you've arrived Masato, and I have to congratulate you on how far you've come, but since you've caught up to where Moriyama was a month or two ago. We can move onto the next stage." Yasuhiro said in his usual gentle tone, with his signature smile on his face.

"Um... So, Yasuhiro-sensei why did you bring us on this mountain at the middle of the night?" Masato said warily he already didn't like the way Moriyama was looking and he hated how the forest looked at night.

"I'll be chasing you down the mountain. If I hit you with this bokken you will be out and will have to alternate between a two hour long plank and a two hour long wall sit for the entire night." Yasuhiro said while smiling.

Masato stared at Yasuhiro for a few seconds thinking he was joking, but seeing him not say anything. He thought that Satow wasn't so bad, at least he didn't literally torture him

"Alright lets begin you have a minute long grace period. Go whenever you want." As soon as Yasuhiro said begin both disciples ran with all their might down the mountain as the counting from Yasuhiro faded the further they got from him, quickly jumping over a branch Masato would feel the ground under him give out as he would begin to fall in a pit trap, but before he could fully fall he would feel someone tug on his hand, looking up he would see Moriyama holding him up while Masato quickly planted his feet along the walls of the pit, and using his other arm pulled himself up.

"Thank you, I thought it was over for me!" Masato quickly inhaled as much air as he could, but the thin mountain air made him feel severely light-headed. Before he could try to talk to Moriyama he saw him continue running. Taking that as his cue to continue he would quickly get up rushing after him.

They had made good progress. At least he thinks they did they decided to stick together that way both could help each other out, and it seemed like they would be fine until Moriyama quickly ducked, Masato thinking there was a projectile trap would duck as well, only to see his teacher come flying out of the brush, with his bokken pointed like a spear in the spot his head previously occupied.

"Run!" Was all Masato could say as both teens quickly got up and ran down the mountain, trying to go as fast as possible while avoiding traps. All while they heard leaves and twigs being cracked behind them, suddenly Masato got pushed by Moriyama sending him tumbling, as he looked he saw Yasuhiro slash vertically while doing a front flip. This confirmed to Masato that the man was definitely trying to kill the both of them. Tumbling through the brush he would come to a stop as he felt his back hit a tree.

"Mori-!" Masato almost blurted out, but he knew that his sensei was nearby, and he couldn't risk giving up his position, so he laid there thinking for a few moments before steeling himself, and would begin to stealthy creep through the brush. He wasn't as fast as Moriyama, nor were his instincts refined, so he would use what he had always needed to use to get out of sticky situations.

Staying low to the ground in a crouching position Masato would use his hands to gently move leaves, twigs, and anything else that could make a noise. Taking his time he would finally see the bottom of the mountain. Letting his thoughts get to him he would spring out the brush and would book it down the mountain, unfortunately he hadn't seen Moriyama trying to signal for him to watch out. As he ran he felt the wind around him change and in his peripheral vision could see a bokken going straight for his head, the next thing he saw was black.

Yasuhiro Residence

Opening his eyes Masato would be irked by the light of the morning sun shining on his face as he slowly registered he was in bed. Quickly getting up he would look around to see Yasuhiro drinking tea at his desk waiting for him to wake up.

"Ah, you're finally awake." The cultivator said as he put down his cup and moved over to Masato. "Anything hurt?" He asked as he smiled at Masato.

"Um, no sir, only a bit sore."

"Good, Well you still got caught so you'll be having to do your penalty tonight." Yasuhiro reminded him of his failure, and judging by the expression on Masato's face he wasn't thrilled to be having to complete his penalty.

"But good news is today you'll be starting your training on total concentration breathing."

"Really? Why hold off for so long?" Masato said. He didn't know why it took so long to reach this point to be honest he was expecting that as soon as he finished the practice swings on the first day he would move to total concentration training

"Well, I didn't know what your skill level was and it's quite advanced to try and learn, plus if you already have a base for swordsmanship without breathing. If you cannot pickup wind breathing then you could try your luck with another breathing style, or even make your own." Yasuhiro informed him while he walked over to the door, opening it before telling him to go to the courtyard once he's ready

Quickly walking out the door he would see Moriyama practicing sword swings while his instructor watched. "So how do you even do total concentration breathing?" Masato asked walking towards the two as he noticed Yasuhiro holding a bokken, unfortunately making him remember the night before.

"You have to breath while your core is relaxed but your arms and legs are tense. Along with breathing in a rhythm of inhale, hold, exhale, hold, each process should be about four seconds." Yasuhiro said as he tapped Moriyama's shoulder and gestured for him to take a break.

"Sounds easy enough..." Masato said as he walked over to Moriyama's old spot and tried breathing, suddenly getting hit in the solar plexus by a bokken. Causing him to fall over as all the air in his lungs left him.

"You weren't doing it correctly you need to envision the air traveling through your body and improving all your muscles." Yasuhiro said as he watched Masato slowly stand back up, a hand on his chest.

"You could've... Told me that before you hit me..." Masato said while taking deep breaths, and tried again. This time he was able to get a record of barely a second as he got hit again with the Bokken.

Courtyard of Yasuhiro Residence

Warm colorful leaves began to fall from the nearby trees. As the cool autumn air washed over a teen who was on the ground as around him he heard wood on wood. Quickly picking up his bokken he would run over to continue fighting coordinating with another boy, with noticeable dark maroon hair that faded to red, he was now standing at 5'6 and while still being slim his musculature was more defined, as he continued to swing, the teen that was just on the ground would take a breath and would rush forward, quickly turning around and back flipping leaping over Moriyama, feeling the air around him contort around his blade he would swing downward. Wind Breathing Ninth Form: Idaten Typhoon.

Yasuhiro, accurately predicting the attack would respond with an attack of his own, Masato watched as he remembered Satow doing the same technique, Yasuhiro would quickly push Moriyama back with his bokken, and would use the surrounding wind to enhance his sword slashes, as he clashed with the gusts caused by Masato's attack, his body being surrounded in a torrent of wind Wind Breathing Third Form: Clean Storm Wind Tree. Masato would watch as both wind attacks hit each other, causing the nearby gales to be nullified, causing the breeze to dissipate as the air would become still.

Moriyama seeing a chance would focus the air into his legs as he rushed forward, as air concentrated around his blade he would slash circularly towards Yasuhiro attempting to hit him head on. Wind Breathing First Form: Dust Whirlwind Cutter.

Yasuhiro feeling the wind pickup would turn his head seeing Moriyama rapidly approaching him, quickly turning towards him he would lift his sword up quickly slashing causing four wind claws to appear and be sent towards Moriyama. Wind Breathing Second Form: Claws-Purifying Wind.

Moriyama seeing the claws would use the wind around him to move him out of the way successfully dodging it but interrupting his attack.

Masato would land behind Yasuhiro, quickly turning he would see an opportunity, rushing at his instructor he would dodge a slash aimed for his throat as he would get under the man, as he would begin to regulate his breathing and felt the wind contort around his sword as he began to use wind-infused slashes to attempt to disarm Yasuhiro. Wind Breathing Fourth Form: Rising Dust storm.

Yasuhiro would be surprised and impressed by the movement, by backflipping he would accurately time Moriyama's attack causing the teen to be tripped by Masato. Both students landing on the ground.

"That was good work by you two today. You both can take a break now." Yasuhiro said as he walked inside, little to no sweat on his body.

It had already been a year since Masato started training and he could now properly use wind breathing forms, but the training was starting to get tedious and he wanted to no when they would be able to attend final selection. Quickly getting up he would walk over to Moriyama. Helping him up as they both went inside.

"Um, sensei, when will be able to attend final selection?" Masato asked, while he sat at a chabudai waiting for Yasuhiro to bring out tea. He began to hear footsteps round the corner as he saw his mentor holding a tray with three cups and a tea pot. "We'll before you can go to final selection you'll have to complete a challenge."

"What's the challenge if you don't mind me asking..." Masato said intrigued he wasn't told that he would have to complete a challenge. Looking over to Moriyama he seemed pretty irked by sensei mentioning a challenge.

"The challenge is to kill five demons." Yasuhiro said with his signature warm smile. "Five demons? That doesn't sound to bad..." Masato said, he was now pretty confused. Seeing as the way Moriyama was looking made him think the worst.

"Where exactly are the demons though? Do you take us to fight them or are we suppose to find them?" Masato asked. Upon setting up the cups across the table, Yasuhiro would sit down and face Masato. "You'll have to find them yourselves, you and Moriyama would be working together for this challenge."

"When do you think we can do this challenge?"

"Whenever you want to. If you really want to you both could leave now." Yasuhiro stated as Masato sat in thought, before turning to Moriyama who was pouring tea into his cup.

"Well, what do you say?" Masato said looking at Moriyama, who after a few seconds, reluctantly nodded. Before writing in his notepad and showing the others.

"We can do it in three days."

"Then it's official, you'll both depart at night on the eleventh." Yasuhiro said. From there the break was silent, no one said anything as they just enjoyed the tea before returning to their rooms.

"I wonder why he was so nervous... I mean he always seemed wary, but he looked visibly irked by the challenge." Masato laid on his bed in thought, deciding to ask him tomorrow he went to sleep.

Yasuhiro Residence Late Night

Rain pattering on the windows of the house could be heard as loud knocking was heard on the front door of the house. Masato, quickly waking up would move to his door, once again he heard the sound of knocking. Moving quickly he would go to the door, but would hesitate. What if it was a demon? He would think about it a little more before deciding if it was a demon, it would've just tore the door down. Opening the door he would see a young boy? girl?, and judging by their height maybe around ten. The most interesting thing being their black hair that faded to a pale turquoise. Wearing a black kimono with scattered turquoise mist symbols.

"Um... Kid, are you lost?" Masato asked while rubbing his eye, he had barely woken up and he was confused on why this kid was in the middle of a storm.

"I'm looking for Yasuhiro-san! Is he here right now? Please! It's important!" The boy? frantically exclaimed. Masato heard a pair of footsteps round the corner, turning he would see Moriyama, standing next to Yasuhiro.

"Yuichiro! What are you doing here in the middle of a storm alone no less!" Yasuhiro said running over as he brought the boy inside.

"Please, Yasuhiro-san you have to help my father! He went to go get some herbs for my mother but... but... He hasn't returned!" The boy now named Yuichiro frantically explained. Yasuhiro nodded and told Moriyama to stay behind and take care of Yuichiro while he and Masato went to try and find the boy's father.

Quickly putting on a coat and shoes, Masato would rush out following Yasuhiro as they both sped off.