"I'm home…"
Yohei barely managed to get the words out as he finally dragged himself through the door, his feet scraping against the floor and his posture slouched. Every muscle in his body protesting against the simple act of standing.
With a tired grunt, he sat down on the steps and tugged off his boots, letting them fall wherever they pleased. Then he leaned back and simply… collapsed, staring up at the ceiling as his breathing slowly evened out.
It took an act of sheer willpower – and the sharp complaints of his stomach – to get him moving again. He hauled himself up and staggered deeper into the house, making a beeline for the kitchen.
Opening the fridge, he was greeted by yesterday leftovers, alongside the many, many containers packed to the brim with boar meat. He considered cooking something for exactly one second before scoffing at the idea. Even reheating the food felt like too much effort.
Instead, his gaze drifted upward.
Popsicles.
He grabbed a handful from the freezer, dumped them into a bowl, shut the fridge, and trudged upstairs toward his room. He peeled one open as he walked, the wrapper crinkling faintly in the quiet house.
"Hm~ Mango…" he murmured.
Kicking the door shut behind him, Yohei collapsed onto the chair by his desk. He closed his eyes, blindly reaching out until his fingers found the switch for the electric fan and flicked it on. Cool air washed over his skin, drawing a low, satisfied hum from his throat.
As the fatigue settled back in, a thought nagged at him.
Why did he feel this exhausted?
By all accounts, today's training had been lighter than the hours he'd spent sprinting after Hayama during their team test. And yet, swimming in the Naka River had felt… heavy. Like the water itself had been resisting him.
He'd played in the river before, further downstream, with other kids. He'd never felt anything like that.
"Something to do with chakra, obviously," he muttered, staring unfocused at a spot on the wall. "But what?"
After a moment, he shrugged. That was a problem for later, he could ask his sensei next time.
He took another bite of his popsicle.
And promptly started to doze off.
…
"Shit!"
Yohei jerked upright, nearly launching himself out of his chair as his heart slammed against his ribs. He clutched at his chest, eyes wide – then froze.
His exhaustion was gone, or at least it felt like it, because under his chest he could feel a buzzing weight, thrumming just beneath his heartbeat.
His breath hitched, then broke into a grin.
"The Chaos Scroll," he laughed under his breath. "I can't believe I almost forgot about it."
He quickly cleared space on his desk, then brought his thumb to his mouth and bit down, drawing a bead of blood.
Boar → Dog → Bird → Monkey → Ram.
He slammed his bloodied thumb against the wood.
Puff.
White smoke burst into the air, and as it cleared, the now-familiar weight of the Chaos Scroll settled into his hands.
This time, he barely spent a moment admiring it before opening the latch and unfurling the paper to see what he would find inside: a single new fūinjutsu seal painted in silver, glowing softly. Without hesitation, he pressed his hand against it.
The familiar sensation washed over him as the Chaos Scroll vanished from his grasp, retreating back into his chest, while another scroll materialized in his hands in its place.
"Nice!" Yohei exclaimed, eyes lighting up.
Differently from the previous ones, this one was neither brown nor gray – instead, it was painted a soft leaf-like green.
Undoing the latches, he muttered a quick, half-serious prayer that if this turned out to be another bloodline, it would at least be less weird than the last one.
Though, if things worked the way he suspected, this would be a jutsu instead. After all, he'd earned this reward by "defeating" his teammates.
And sure enough, the first words he read confirmed it.
[水の呼吸 – Mizu no Kokyū – Water Breathing]
| C-Rank Manual |
Water Breathing is a specialized swordsmanship style and breathing technique that mimics water – its flow, flexibility, and adaptability – and replicates it through the user's movements, techniques, and abilities. Most known forms involve fluid body motion and seamless transitions of arms and weapon alike, mirroring rushing streams or flowing currents. Through the use of Chakra Flow and Nature Transformation, water may be manifested to further augment the style.
Yohei's eye started twitching.
He had to physically restrain himself from screaming.
"Son of a–" he hissed, clamping a hand over his mouth and swallowing the rest of the curse. "Really? Really?"
The irony was almost malicious.
Just hours after his sensei had asked them what they wanted to specialize in – after he'd gone through a whole internal monologue about focusing his path, narrowing his options, and not overloading himself with unnecessary techniques – this was what he got.
Water Breathing was perfect for him in so many ways.
Water affinity. Body techniques. Adaptability.
And then there was the problem.
It was swordsmanship.
"What now?" he groaned, dragging a hand down his face.
He couldn't exactly show up tomorrow and tell Hayama-sensei that he'd changed his mind and now wanted to focus on kenjutsu instead of taijutsu. The man would think him fickle, indecisive – probably scold him for wavering so easily.
"I should've opened it earlier," Yohei muttered bitterly. "All I had to do was say I needed to go to the bathroom at the restaurant."
Then again… maybe not.
Maybe his sensei wouldn't see it as a flaw. Maybe he'd just see a kid still testing his options, still figuring himself out.
But even if Hayama did agree to teach him swordsmanship, it would be Hayama's style. Not this.
And how would Hayama-sensei react if, after lessons, Yohei started unconsciously – or deliberately – showing movements and forms that clearly weren't part of the style he'd been taught?
How could he not suspect that Yohei was getting instructions somewhere else?
Letting out a long groan, the accumulated stress finally caught up to him. Yohei tossed the scroll back onto the table and started scarfing down popsicle after popsicle in a futile attempt to drown his thoughts in sugar and cold –
– until he suddenly winced, clutching his head.
"Ah – shit – brain freeze…"
He leaned back in his chair, rubbing his temples, then drummed his fingers against the table as his gaze drifted back to the scroll. His expression slowly shifted from irritation to confusion.
Then realization hit.
"Wait a minute," he muttered, leaning forward. "Isn't this–"
He picked the scroll back up and reread the description carefully.
"…Isn't this from Demon Slayer?"
Demon Slayer, or Kimetsu no Yaiba was another anime from his alternate life, the same as Naruto, though he'd never actually finished it for lack of time.
"Does that mean everything I've gotten so far came from some anime?" he asked himself, intrigued. "Or… maybe not just anime. Other kinds of media?"
The thought sent a spark of excitement through him, and a grin tugged at his lips.
"Wait – doesn't that mean there could be a Bloodline Limit out there that turns me into a Saiyan?"
He indulged the fantasy for exactly three seconds before snorting and shaking his head.
"As if. That'd be, what, an A-Rank reward? Higher?" He scoffed. "Even a low-class Saiyan can blow up a moon. That's already a feat that borders the ceiling of power in this world."
Still, the implication lingered.
The Chaos Scroll could pull things from fiction.
Techniques, powers, bloodlines – concepts from entirely different worlds flickered through his mind, and he left himself get lost in the possibilities for a moment.
Then his brow furrowed.
He looked back down at the scroll, rereading the final lines more carefully.
Through the use of Chakra Flow and Nature Transformation, water can be manifested to further augment the power of the style.
"…That's not how it worked in the anime," Yohei muttered.
He remembered with some fondness the arguments from old versus forums – the copium, the memes, the outright denial – whenever someone pointed out that the flashy elemental effects in Demon Slayer weren't real. Just visual metaphors. Stylized delusions. Shōnen schizophrenia.
There was no actual water.
But this?
This explicitly said water could be manifested.
If that was true, then only two possibilities he could think of made sense.
One:
This world wasn't just a Naruto world like he'd assumed – it was a crossover. Somewhere out there, there might exist samurai analogues who had genuinely developed breathing styles, real ones, integrated into the world's history.
The thought left an uncomfortable knot in his chest.
Had that always been the case?
…Or had the Chaos Scroll changed reality to make it so?
Or two:
Everything he obtained through the Chaos Scroll was being adapted to fit this world – and its power system. Namely, chakra.
Thankfully, Yohei was almost completely certain that this was the correct answer, especially when he considered how the Chaos Scroll itself had changed. What had once been a gamer-like interface had become, quite literally, a scroll. He had even seen the same thing happen with Mugetsu when he'd first read her description.
"So an Ōzaru would be something like a broken Sage Mode?" he mused aloud, amused, before shaking his head again.
Focus.
If this really was Water Breathing from Demon Slayer, then-
"Yep," he said with sudden glee. "Here it is. Total Concentration Breathing."
The first portion of the scroll wasn't actually about Water Breathing itself, but rather a breakdown of its foundational components. A list of prerequisites, followed by instructions on how to acquire and master the essential core upon which all breathing styles were built.
"Total Concentration Breathing is the cornerstone of every breathing style. It is a taijutsu technique whose principle lies in the super-expansion of an individual's lungs in order to intake the maximum amount of oxygen possible. This process accelerates the body's blood flow, increases heart rate and body temperature, and energizes bones and muscles alike – granting the user superhuman physical characteristics.
"Among the abilities granted through the mastery of Total Concentration Breathing are superhuman strength, speed, stamina, durability, endurance, and the enhanced mental faculties required to keep up with such a body – such as accelerated thought processes and reaction time.
"One who has mastered Total Concentration Breathing will find their strength sufficient to slice through boulders and trees, generate whirlwinds with a single swing, effortlessly shatter the bodies of their foes, and lift weights many times their own with bare hands.
"One who has mastered Total Concentration Breathing will find their speed sufficient to outpace the fastest of horses, moving so quickly that the human eye cannot perceive them.
"One who has mastered Total Concentration Breathing will find their stamina and endurance sufficient to engage in constant combat for an entire week without food, water, or sleep under extreme conditions, emerging even stronger after a period of rest.
"One who has mastered Total Concentration Breathing will find that they have become both demon… and demon slayer."
Yohei finished reading with barely contained excitement.
All things considered, aside from the absurd stamina, this wasn't that much stronger than what a competent chūnin should already be capable of. Impressive, yes – but not world-shattering.
No.
The interesting part was something else entirely.
Up until this point, the scroll hadn't mentioned chakra once.
Which meant this was a wholly physical technique – something that didn't rely on chakra circulation at all.
Something that even chakra-inapt civilians could theoretically learn.
And also –
"Just imagine this coupled with Chakra Enhancement," he muttered in awe. "If a regular – if well-trained – body already becomes superhuman when augmented by chakra, how much stronger would someone who's already superhuman become? And how would that even compare to the Eight Gates?"
He had no idea.
But he was very eager to find out.
Yohei turned his attention back to the scroll. What followed was a long series of instructions detailing a variety of training methods that could be used in conjunction to prepare an individual for the technique, depending on their circumstances and available resources.
"Aerobic exercise at high altitude… confinement in areas with limited airflow… submerged meditation…" The next one made him chuckle. "Swimming against strong currents, waterfall training – and of course, gourd blowing."
All of it – and more besides – was designed to condition both body and mind in preparation for the actual breathing technique. That method was laid out in excruciating detail, accompanied by dense diagrams and anatomical illustrations that filled the page.
Contrary to his expectations, however, what came next wasn't the sword forms of Water Breathing.
It was more.
Further instruction on the mastery of Total Concentration Breathing itself.
"The use of Total Concentration Breathing during brief moments of conflict or necessity already turns its user into a monster among men – but this is not true mastery.
"A true master of Breathing is one who lives in such a state constantly: morning, noon, and night, even while eating and sleeping. From this is born Total Concentration: Constant. Zen Shūchū Jōchū.
"The difference between a true master and a novice is like that of heaven and earth. Every aspect of the body and mind that is enhanced by the base form of Breathing is further amplified to such a degree that a master may treat a common user as casually as a common user treats an ordinary man.
"Such a state cannot be achieved without tremendous effort – even if the complexity of the act itself is no different from what was required to learn the base form. There is no secret. No trick.
"Only do more, for longer, until you reach your limits – and then break past them.
"Kill yourself in a thousand ways, and then pick up your corpse a thousand times more, until all weakness has been beaten from you, and all that remains is a slayer, with a body made to breathe."
Despite the brutality of the description, a structured framework lay beneath it – a series of guidelines, clear and methodical instructions outlining how a user who had already achieved Total Concentration Breathing could transition into its Constant state, tailored according to the training methods they had previously employed.
There were also new exercises listed.
Exercises so demanding that only someone who had already pushed their body to that extreme level of conditioning could even attempt them.
The scroll went even further, detailing two additional variants of the base technique: Enhanced Recovery and Recovery Breathing – Kaifuku no Kokyū.
The first focused on increasing the practitioner's awareness of their own body through breathing, to the point where they became capable of sensing their organs, muscles, and blood flow directly. This heightened perception allowed them not only to detect injuries and foreign substances such as poison, but also granted a degree of conscious control over their own biology.
With it, they could coagulate blood to stop bleeding, slow circulation to delay the spread of toxins or feign death, and consciously direct energy to specific areas of the body to accelerate healing.
The second technique, however, was just as intriguing – and far more unsettling.
It revolved around using oxygen as the body's primary "battery," replacing nutrition as the main source of energy. Through precise breathing, the practitioner could substitute rest and feeding with oxygen intake, restoring their body to peak performance if given enough time to employ the technique – or push themselves through even more extreme stretches without any form of rest at all.
"This is insane," Yohei muttered with a slightly disbelieving chuckle, a twisted smile tugging at his lips. "What the hell is this? Is this actually canon in that world, or is the Chaos Scroll just adding things now?"
He shook his head, half-laughing. "This is just discount magical self-biokinesis. At this point, the only difference between a Demon Slayer and a Demon is the ability to generate biomass, isn't it?"
Only after all of that did the scroll finally turn to Water Breathing itself.
It laid out the Forms in excruciating detail – from the First through the Eleventh, including many variants – explaining not only the physical movements, but the mindset that needed to accompany each one to draw out its full potential. Alongside them were meditative practices meant to cultivate the insight required to truly grasp each Form.
And then came the final section.
A guide on Chakra Flow, followed by introductory instructions on Nature Transformation, explaining how the two could be combined with Breathing to achieve the complete, perfected state of Water Breathing.
"I can use this," Yohei said with a grin that bordered on feral. "I can definitely use this. Even without a sword – even if Water Breathing itself wasn't included – just the potential of Total Concentration Breathing alone would have been enough."
The time it would take him to train his body for the first stage, along with learning the breathing method itself, would be more than enough for him to plausibly pass it off as a technique he had developed through experimentation and refinement.
Hell, he could even adapt Water Breathing into a taijutsu style instead of a kenjutsu one.
That thought made him pause, something familiar tugging at the back of his mind – something he'd heard recently, and the way it had made him feel at the time.
It wasn't quite the same, but…
He snorted.
"You were wrong, Souma. It's not swords – it's fists that are the best."
Speaking of Souma – and his teammates in general – this was something he would definitely teach them once he had finished training himself.
Even without even touching on how much the sheer physical and mental improvements brought about by the technique would naturally increase their chakra reserves-
How much would Ren benefit from this, when stamina was his biggest weakness right now?
How much more of a monster would Souma become if he somehow turned out even faster than he already was?
And beyond that – could they develop their own Breathing Styles?
It wasn't as if being taught by Yoriichi was a requirement, after all. You didn't even need prior exposure to another Breathing Style – hadn't Inosuke created his entirely on his own in a mountain?
The possibilities made Yohei's fingers twitch, barely resisting the urge to start training right then and there.
But he was also –
"Tired as fuck," he muttered with a crooked smile, laughing softly at himself. "There's no way I'd get anything useful done like this."
Tomorrow, though.
Tomorrow he'd start as early as possible.
For now, he rolled the scroll back up and, with visible reluctance, stored it away in a safe place. Then he returned to his table, picked up one of the books from the pile, and opened it to a marked page – feeling his spirits lift when he realized he was already more than halfway through.
"Back to the grind."