Demon Slayer: Dragon Hashira#4+5+6: Doubts and Deductions, Tamayo, Yushiro's Request & Urokodaki's Recognition

The moment the third possibility crystallized in his mind, Kaidō felt a chill run down his spine.

The very notion was absurd—every member of the Demon Slayer Corps harbored a blood-deep hatred for demons. How could they possibly slaughter an innocent family? Yet the more he examined the theory, the more the pieces began to fit together in ways that made his stomach turn.

If we eliminate the impossible, whatever remains—however improbable—must be the truth.

Setting aside Muzan Kibutsuji's ability to create demons, it was theoretically possible the Demon Slayer Corps had also developed that capability. Pure speculation, yes, but not beyond the realm of possibility.

Over a thousand years, the Hashira had slain countless members of the Twelve Kizuki. The Corps would have access to blood samples with high concentrations of Muzan's essence. They possessed combat abilities far beyond ordinary humans. They even kept demons imprisoned for research purposes.

But the most damning piece? Motive.

The emergence of a successor to Yoriichi Tsugikuni—the legendary first Breathing Style user—would pose a legitimate threat to Muzan's existence. The Demon King himself would fear such a warrior.

Kaidō wasn't suggesting every Corps member was complicit. His suspicions centered on one man: Kagaya Ubuyashiki, the Corps' master.

Kagaya had willingly sacrificed his wife and two of his children just to wound Muzan—a calculated move that spoke to ruthless pragmatism. Even Muzan had described Kagaya as "a cold, dangerous snake." High praise from a monster who'd lived for centuries.

There was no question that destroying Muzan was Kagaya's singular obsession. He would employ any means necessary to forge a swordsman capable of ending the Demon King's reign.

The strongest warriors in the Corps all share one trait: they harbor hatred for demons that burns hotter than hellfire itself.

To mold Tanjiro Kamado into such a weapon, Kagaya would first need to fill him with that same all-consuming rage. Which meant creating a tragedy so devastating it would reshape Tanjiro's entire existence.

So he killed them. Or had them killed.

As for why Nezuko was transformed into a demon—that was where the theory became truly disturbing.

The Ubuyashiki family had operated the Demon Slayer Corps for a millennium. Surely they'd conducted private research into Muzan's blood over the centuries. What if Nezuko had been selected as a test subject? That would explain why she alone among countless demons exhibited such unique characteristics.

Countless demons had retained fragments of their humanity, but not a single one had managed to resist consuming human flesh. None had achieved what Nezuko accomplished.

The appearance of Water Hashira Giyu Tomioka seemed to validate the hypothesis. Why would a Hashira just happen to be near the Kamado residence? Giyu had offered no explanation for his presence, but his focus on Nezuko had been unmistakable.

Giyu himself might have been oblivious to the larger machinations, but Kagaya could have orchestrated everything—a calculated gamble that modified Muzan's blood would prove effective.

Moreover, Giyu's timely arrival seemed explicitly designed to recruit Tanjiro into the Corps. But how had Giyu even known demons were at the Kamado household?

The Kasugai Crows.

Demons lurking in remote mountain regions rarely generated intelligence reports. Other demons Tanjiro had encountered in the wilderness went completely unnoticed by the Corps. Yet Giyu's crow had somehow delivered precise information about the Kamado residence.

The crows were trained exclusively by the Ubuyashiki family.

Another piece clicks into place.

Furthermore, the Ubuyashiki family had likely known for years that the Hinokami Kagura—the Dance of the Fire God—was preserved within the Kamado lineage. Just as Kagaya's wife, Amane Ubuyashiki, had located the descendants of Michikatsu Tsugikuni (now Upper Rank One, Kokushibo)—specifically, Muichiro Tokito, the current Mist Hashira.

While the Ubuyashiki family maintained historical records, those archives were neither comprehensive nor entirely intact. Despite this, they'd successfully traced bloodlines that had been lost for generations. If they could find completely disconnected descendants of the original swordsmen, locating the inheritors of the Fire God Dance would be trivial by comparison.

Another detail demanded attention: Why did Kagaya show such particular interest in these siblings? Why invest so heavily in Tanjiro's development while displaying no surprise whatsoever at Nezuko's condition?

The other Hashira's reactions spoke volumes—they'd been ready to execute both siblings on sight. Yet Kagaya had remained eerily calm, almost as if he'd expected everything.

A man capable of sacrificing his own family to kill Muzan would stop at nothing. It's a form of righteousness—and a form of cruelty.

Kaidō's thoughts twisted through the labyrinth of conspiracy, each connection leading to darker implications.

"But these are just theories. Speculation built on circumstantial evidence and paranoid pattern-recognition. What if I'm wrong? I'd be vilifying an innocent man who's devoted his life to protecting humanity."

Yet if he was right...

"Forget it." Kaidō exhaled slowly, forcing his racing thoughts to settle. "No use spiraling down rabbit holes I can't escape. When in Rome, as they say—or in this case, when in Taisho-era Japan. One step at a time."

His more immediate concern was practical: he'd overstayed his welcome.

"I need to leave soon. I've been here too long already. The Kamados have been incredibly generous—they'd never complain—but I can't keep imposing on their hospitality forever."

The thought triggered an unwelcome memory from his third day here. He'd been preparing to bathe when he'd entered the washroom and found Nezuko—completely naked—about to step into the tub.

God, that was mortifying...

They'd managed to clear up the misunderstanding, and Nezuko hadn't blamed him, but for several days afterward, both of them would flush crimson whenever they made eye contact. Kie Kamado had started giving them knowing looks, clearly suspecting some budding romance.

It had taken considerable effort to dispel that notion and restore normalcy between them.

'And why the hell am I thinking about that again? She's a child, for crying out loud. That's a one-way ticket to prison—three years minimum, death penalty maximum.'

Although, he had to admit, modern prisons weren't so bad. Three meals a day, running water, and if you were lucky, you might even find some soap in the shower—

"What the hell is wrong with me? These thoughts are getting progressively more disturbing." Kaidō scrubbed his face with both hands. "Focus. I need to prepare to leave, but I can't let Tanjiro and the others know I'm going."

"Kaidō-nii! Dinner's ready!" Hanako's cheerful voice called from outside.

"Coming, Hanako!" He rose to his feet and stepped outside, immediately ruffling the young girl's hair affectionately.

"Kaidō-nii, if you keep messing up my hair like that, I won't have any left!" Hanako protested, though her face was bright red.

"Don't worry, you'll be fine. Besides, you're going to grow up into an absolutely adorable young lady." He took her hand and started walking toward the house.

"Kaidō-nii, after dinner, can you tell us more stories? I love hearing your stories!" Hanako's eyes sparkled with anticipation.

"Sure thing. Whatever stories you want to hear tonight, I'll tell them."

"Yay!"

.....

The next morning, Kaidō rose well before dawn. He gathered his belongings—though "gathering" was generous, since his system's storage space held everything of value. He traveled light.

He placed a handwritten letter and fifty yen into an envelope. Fifty yen was pocket change to him, but for the Kamado family, it represented several months' worth of living expenses—enough to significantly improve their quality of life.

He deliberately avoided leaving more, knowing they'd refuse to accept it. They probably wouldn't even spend what he'd left, instead saving it to return to him when they next met.

Without disturbing anyone, Kaidō slipped out of the warm little house that had sheltered him.

...

"Kaidō-san, time to wake up! Breakfast is ready... Kaidō-san?" Tanjiro knocked on the door but received no response. He slid it open to find the room empty—only a letter resting on the table.

"Father, Mother—Kaidō-san left!" Tanjiro brought the envelope to where Kie was tending to Tanjuro.

When Tanjuro opened it, he discovered not just a letter, but fifty yen.

Tanjuro-san, Kie-san, Tanjiro, Nezuko, Hanako, Takeo, Shigeru, and Rokuta—thank you for everything during my stay.

Thank you for welcoming me as part of your family. But all good things must come to an end, and I have responsibilities I can no longer postpone.

Please accept this money—not as payment, but as a token of my sincere gratitude. If fate permits, I'll come visit again someday.

Tanjuro carefully refolded the letter and handed the money to Kie.

"That boy has a good heart. I hope he stays safe out there. I hope his future is bright." Kie's voice was soft with genuine concern.

"It will be," Tanjuro said with quiet certainty. "I can sense it—he's destined for extraordinary things. And I have a feeling Tanjiro will see him again sooner than we think."

From the moment Tanjuro had first met Kaidō, he'd known the young man was no ordinary person. The look in his eyes told a story—sorrow, regret, weariness, and beneath it all, a strange composure. He carried himself with a presence that didn't match his apparent age.

...

"Where the hell am I??"

After leaving the Kamado residence, Kaidō had wandered aimlessly for several days like a man without a map or compass. Now he found himself standing in a bustling town decorated with lanterns and festive banners, completely and utterly lost.

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"Well, this is just great. I'm completely lost."

Kaidō stood at the intersection of brightly lit streets, lanterns casting warm glows across the festive decorations. Every direction looked identical—a maze of unfamiliar roads leading to unknown destinations.

He tried asking for directions, but the moment people caught sight of his unusual appearance—the flowing white hair, the golden eyes, the strange clothing—they gave him a wide berth, as if proximity alone might curse them with misfortune.

Worse still, while cutting through an alley earlier, he'd been accosted by a group of drunk idiots.

"Well, well, well... hic... what do we have here? Such a pretty little lady... hic... walking alone in a dark alley this late at night. Very dangerous, you know? hic How about I escort you home? Or better yet... hic... you could come to my place instead. Hehehe!"

The rage had been immediate and overwhelming.

Kaidō had used what he generously estimated as "a tiny bit" of force to flatten all of them. Then he'd walked away. But the more he thought about being called "little lady," the angrier he became.

'I'm a grown-ass man, for god's sake...'

Well, okay, a five-foot-tall "grown man."

Still.

The indignity burned so fiercely that he'd marched back and delivered several well-placed kicks to their... sensitive areas. The drunks had passed out from the pain, and for good measure, Kaidō had stripped them naked and dumped their clothes in a garbage heap several streets away.

"I just wanted directions," he muttered to himself. "Why does everything have to be so complicated?"

He exhaled slowly, centering himself. "Alright, one more try. If this doesn't work, I'll just have to figure it out myself. Dammit system—would it kill you to provide a map or at least a compass??"

Kaidō had a destination in mind: Mount Sagiri, where he intended to seek out Sakonji Urokodaki and eventually participate in the Final Selection on Mount Fujikasane.

Two reasons drove this decision.

First, he needed to strengthen himself. Second, the system had finally issued a quest after its extended silence during his time with the Kamados.

Apparently, the system had been undergoing an upgrade for the past two weeks—hence the lack of missions. Now that the upgrade was complete, it had dropped this task in his lap the moment he'd left the Kamado residence.

[Quest: Journey to Mount Sagiri and seek training from Sakonji Urokodaki. Participate in the Final Selection.]

[Rewards: Phantom Eye, Mental Enhancement Serum x2, Dragon Breathing Seventh Form, Dragon Breathing Eighth Form, 100,000 Yen.]

Phantom Eye — Nullifies all illusionary techniques and prevents mental manipulation. Can also trap enemies within illusions. The stronger the user's mental fortitude, the longer the duration of control.

Mental Enhancement Serum — Strengthens mental resilience and sharpens cognitive function. Greater mental strength equals stronger willpower and clearer strategic thinking.

Dragon Breathing, Seventh Form: Eight-Directional Blitz — With the user as the epicenter, unleash devastating sword strikes in all eight cardinal directions simultaneously. The faster the blade, the more projections generated. Scales with the user's combat prowess.

Dragon Breathing, Eighth Form: Serpent's Pierce — Linear assault technique. Draw the blade and strike forward at blinding speed, like a dragon lunging through water. The stronger the user, the faster the execution—enemies fall before they can even register the attack. (Inspired by Hakurou from That Time I Got Reincarnated as a Slime.)

Kaidō mentally reviewed the rewards with satisfaction.

"The Phantom Eye will be invaluable if I run into demons who use mental manipulation Blood Demon Arts—like Lower Rank One, Enmu. Perfect counter."

"The system was going to reward all four remaining Dragon Breathing forms, but since I developed the Fifth and Sixth Forms myself, it substituted the Mental Enhancement Serums instead. Fair trade."

"The Seventh Form is a defensive-offensive hybrid—perfect for when I'm surrounded. Even if enemies close the distance, they'll take catastrophic damage trying to breach the blade storm."

The Eighth Form is pure assassination—blink and your opponent's already in pieces. Merciful, in a way. They won't even feel it.

"As for the money... I haven't even spent the last reward yet."

His stomach chose that moment to growl loudly.

"Right. Can't exactly journey to Mount Sagiri on an empty stomach." He glanced around. "Food first, then navigation."

Finding a food stall in this upscale district proved more challenging than expected, but eventually, he spotted one—a small ramen stand operated by a bald man puffing on a pipe.

Kaidō froze mid-step.

Wait a second. Why does this guy look so familiar?

Realization struck like lightning.

This is the noodle stand from the anime! The one Tanjiro visited with Nezuko after she became a demon. Which means... this is where Tanjiro encountered Muzan Kibutsuji. And after Muzan fled, Tanjiro met Tamayo here.

His mental gears clicked into place.

'That means I'm in Asakusa!'

"Boss! One bowl of yam udon!" Kaidō called out, sliding onto a stool.

"Coming right up, customer!" The bald proprietor sprang into action, his movements practiced and efficient.

Minutes later, a steaming bowl appeared before him.

"Here you are! Enjoy!"

"Slurp—mmm—huff—this is excellent! The broth especially!" Kaidō's genuine enthusiasm broke through his exhaustion.

"Ah, you've got a good taste, young customer! This recipe has been passed down through my family for generations..." The owner launched into an enthusiastic explanation of his culinary heritage, clearly delighted by the praise.

...

"Thanks, boss. Keep the change—the food was great." Kaidō placed his payment on the counter and stood.

"Thank you! Please come again!"

After leaving the noodle stand, Kaidō resolved to find one more person to ask for directions. If that failed, he'd navigate to Mount Sagiri on his own, even if it took weeks.

That's when he spotted them—two figures standing in a sparsely populated side street.

Not people. Demons.

The woman wore an elegant purple kimono adorned with floral patterns, her hair styled in an intricate updo. Purple eyes regarded the world with calm intelligence—a mature beauty who carried herself with quiet dignity.

Beside her stood a young man with green hair and a perpetually hostile expression, as if the entire world had personally wronged him. He positioned himself like a guard dog, snarling at anyone who dared approach the woman.

In his eyes, only she existed. Only she mattered.

Tamayo and Yushiro.

"Well, that's convenient," Kaidō murmured. "I can ask them for directions to Mount Sagiri. But if I just call them by name, they'll get suspicious..."

An idea crystallized.

'Wait. There's something I could tell them—something that might convince Tamayo to help me.'

He approached directly.

"Excuse me. Sorry to bother you, but could I ask for directions?"

"Get lost! Don't you dare come near Lady Tamayo!" Yushiro's voice crackled with aggression.

"Yushiro, that's incredibly rude!" Tamayo's rebuke was gentle but firm.

"Yes, Lady Tamayo." His tone shifted immediately to one of reverent obedience.

'Even when Lady Tamayo scolds me, she's beautiful,' Yushiro thought dreamily.

"I apologize for my companion's behavior," Tamayo said, turning to Kaidō with a warm smile. "He means no harm—his temper simply runs hot. How may I assist you, young miss?"

"Hmph. Ugly girl," Yushiro muttered under his breath.

Kaidō's eye twitched. "Uh, actually... I'm a guy."

Tamayo blinked. "Oh! My apologies. Your features are quite... delicate. I mistook you for a young woman. Now then, how may I help you?"

"I'm trying to find the way to Mount Sagiri. I need to visit someone there and participate in the Final Selection on Mount Fujikasane."

Yushiro's expression transformed from irritation to alarm.

"Lady Tamayo, run! I'll hold him off!" He lunged forward, fist cocked back.

Kaidō sidestepped the telegraphed punch with almost insulting ease. The fist passed within an inch of his face. In one fluid motion, he caught Yushiro's arm, pivoted, and executed a textbook over-the-shoulder throw.

THUD.

Yushiro hit the ground hard. Kaidō planted one foot on his back, pinning him in place.

For someone who'd consumed the Body Enhancement Serum and mastered Total Concentration Breathing: Constant, Yushiro's attack had been laughably slow—like a toddler throwing a tantrum.

"I mean no harm," Kaidō said calmly, addressing Tamayo. "I only want directions to Mount Sagiri so I can train and join the Demon Slayer Corps. After all, you'd like nothing more than to avenge your husband and children by destroying Muzan Kibutsuji—wouldn't you, Lady Tamayo?"

The temperature seemed to drop several degrees.

Tamayo's expression remained serene, but her eyes sharpened with sudden intensity. "This isn't the place for such conversations. Please, come with me. And could you release Yushiro? He's only trying to protect me. Surely you understand."

"Of course." Kaidō stepped back, allowing Yushiro to scramble to his feet.

Yushiro immediately positioned himself between Kaidō and Tamayo. "Lady Tamayo, this person is definitely suspicious! He must be one of Muzan's assassins. Or even if he's not, he's definitely a Demon Slayer. We can't trust him!"

"Yushiro, I'll make my own judgments. Besides..." Tamayo's gaze lingered on Kaidō with unsettling accuracy. "If he intended to kill us, I doubt we'd survive the encounter."

"This gentleman is...?"

"Ryūjin Kaidō."

"Then, Kaidō-san, please follow me."

...

They approached what appeared to be a solid wall. Tamayo and Yushiro walked through it as if it were made of mist. Kaidō followed, stepping into the hidden courtyard beyond.

The illusion concealed a modest mansion—elegant in its simplicity, yet clearly designed with care.

I knew about this from the anime, but seeing it in person is something else entirely.

They entered the main hall and settled into the sitting area.

"That wall back there," Kaidō said casually, "was Yushiro's Blood Demon Art—Blindfold, correct?"

Yushiro stiffened. "How did you—"

"It seems you know quite a bit about us, Kaidō-san," Tamayo observed.

"I know you were turned into a demon by Muzan without your consent, and that you killed your own husband and children before you even understood what had happened. I know you encountered Yoriichi Tsugikuni—the first Breathing Style user—and that he helped free you from Muzan's control."

Kaidō's voice remained steady, almost clinical.

"I know you possess the ability to transform humans into demons, but you always ask for their consent first. Yushiro is proof of that. I know you don't consume human flesh—you purchase blood from people in need, offering them money in exchange. I know you have exceptional medical knowledge and have dedicated yourself to researching ways to destroy Muzan."

He leaned forward slightly.

"And I know the only thing you truly want in this world is revenge."

Silence hung heavy in the room.

Yushiro's hands clenched into fists. "Lady Tamayo, you see? He's definitely sent by Muzan to eliminate us! Even if he's not, he's planning something!"

"Yushiro!" Tamayo's sharp tone froze him in place.

"Yes, Lady Tamayo."

He sat rigidly, though his inner monologue continued. 'Even when she's angry, Lady Tamayo is breathtakingly beautiful.'

Tamayo turned back to Kaidō, her expression unreadable. "If you didn't possess human body temperature, human scent, and a human heartbeat, I would be convinced you were one of Muzan's demons. Your knowledge is... troubling."

"So will you help me?" Kaidō asked. "And in exchange, I'll grant you one favor. Any request within my power. How does that sound?"

...

"I can agree to that." Tamayo's voice was measured, contemplative. "Though I confess, I don't understand how you know so much about us. But everyone has their secrets, and I respect that."

She folded her hands in her lap. "My condition is simple: I need you to collect blood samples from the Twelve Kizuki whenever possible. Their blood is closest to Muzan's in composition, which makes it invaluable for my research."

"Done." Kaidō didn't hesitate. "We have a deal."

"Yushiro, please show Kaidō-san to a guest room."

"Yes, Lady Tamayo."

They walked in silence down the corridor, footsteps muffled against tatami mats. Kaidō waited until they'd put some distance from the sitting room before speaking.

"Why don't you just tell her?"

Yushiro stopped mid-stride. "Tell her what?"

"How you feel, you moron." Kaidō's tone was almost conversational, which somehow made it sting worse. "You're so obviously head-over-heels for her that it's painful to watch."

"That's... I don't... you have no right...!" Yushiro's face flushed crimson beneath his green hair.

"No right? Really?" Kaidō turned to face him fully, golden and purple eyes boring into Yushiro with uncomfortable intensity. "Listen, if you can't even tell the woman you love how you feel, what happens when it's too late? When she's gone and you never got the chance?"

His voice dropped lower, taking on an edge that suggested personal experience.

"It's better to say it now and risk rejection than to live with regret for the rest of your existence. At least if she turns you down, you'll know. You won't spend the rest of your life wondering 'what if.' You won't have that weight crushing your chest every time you think about her."

Yushiro opened his mouth to argue, but Kaidō wasn't finished.

"And I'll tell you something else—something you need to hear whether you want to or not. One day, Tamayo is going to sacrifice herself to destroy Muzan. She'll throw her life away for revenge, and when that happens, it'll be too late to tell her anything."

The words hit like a physical blow. Yushiro actually staggered back a step.

"You're lying—"

"I'm not." Kaidō's expression softened slightly, genuine sorrow flickering across his features. "Believe me or don't—that's your choice. But I know what it's like to lose someone before you could say what needed to be said. I know what it's like to realize you'll never get another chance to—"

His voice caught. For a moment, the mask slipped, and Yushiro saw raw pain in those mismatched eyes.

"I can't be with my family anymore," Kaidō finished quietly. "My mother. My sister. I'll never get to tell them..." He trailed off, shaking his head. "Don't make the same mistake I did."

Silence stretched between them, heavy and uncomfortable.

...

"We're here." Yushiro's voice had lost most of its hostility. "This is your room for the night. Get some rest."

Maybe it was Kaidō's words—the genuine emotion behind them—or maybe Yushiro just recognized a kindred spirit in pain. Whatever the reason, his attitude had shifted from outright hostility to grudging neutrality.

"Thanks." Kaidō moved toward the doorway, but Yushiro's question stopped him.

"Is it true? What you said about Lady Tamayo?"

Kaidō didn't turn around. "I can only tell you this, Yushiro: don't let yourself have any regrets. Whatever you need to say, say it while you still can."

...

The Next Morning

Yushiro arrived at Kaidō's room carrying a breakfast tray and a small travel pack. He set the food on the table, then held out the bag.

"Lady Tamayo asked me to give you this. It's got a map to Mount Sagiri, some travel money, and dried provisions. Follow the route marked on the map and you'll reach your destination."

"Thanks. Tell Tamayo-san I appreciate everything."

Kaidō reached for the pack, but Yushiro didn't release it immediately. The demon's expression was conflicted—like he was wrestling with something internally.

"Can I... ask you for a favor?"

"Depends on what it is. But if it's something I can actually do, sure."

The night had been long. Yushiro had spent hours lying awake, turning Kaidō's words over and over in his mind. The thought of Tamayo sacrificing herself—of losing her without ever expressing what she meant to him—was unbearable.

He'd made a decision. Whatever it took, even if he had to trade his own life, he would make sure Tamayo survived.

"Tell me..." Yushiro said, voice barely above a whisper. "Tell me how to stop Lady Tamayo from sacrificing herself to destroy Muzan."

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"Tell me how to stop Lady Tamayo from sacrificing herself to destroy Muzan!"

Kaidō's expression remained carefully neutral. "There are certain things I can't reveal—not because I won't, but because speaking them aloud might trigger consequences I can't predict or control."

He leaned forward, his golden eyes meeting Yushiro's with unwavering intensity.

"But I can promise you this: I'll find a way to help Lady Tamayo get her revenge without sacrificing herself. However, I'll need your cooperation—your silence, specifically. If we mishandle this and create an irreversible chain of events, it won't just be Lady Tamayo who dies. You'll go down with her."

"Then tell me what I need to do!" Yushiro's voice cracked with desperation. "I'll do anything—ANYTHING—as long as she survives."

"Listen carefully." Kaidō's tone shifted, becoming almost hypnotic in its certainty. "If you're willing to trust me, then what I'm asking is simple. Pretend this conversation never happened. Continue your daily routine exactly as before. Don't question Lady Tamayo. Don't try to stop her research."

His voice dropped lower, each word deliberate.

"Her research must be completed if we want to save her life. Your job is to wait. When the time comes, I'll contact you and tell you exactly what to do. But until then—and I cannot stress this enough—you must act as if nothing has changed. Business as usual. No deviations."

Yushiro's brow furrowed. "That's it? Just... keep living normally?"

"That's it. That's all you can do."

"And you're certain this will work?"

"I'm certain it's the only path forward," Kaidō replied, which wasn't quite the same thing but would have to suffice.

Yushiro studied him for a long moment, searching for deception and finding only resolve. "Fine. I'll trust you—for now. But if you're lying to me, if anything happens to Lady Tamayo because I stood by and did nothing—"

"It won't come to that."

'I know how the story unfolds,' Kaidō thought. 'And even if something changes, I have the system as a failsafe. The real question is whether my interventions will trigger a butterfly effect that spirals beyond my control.'

...

"Finally. About damn time."

Kaidō stood at the base of Mount Sagiri, craning his neck to take in the mist-shrouded peaks. Thick clouds of fog rolled down the mountainside like ghostly waterfalls, obscuring everything beyond a few dozen feet.

"At night, this place must be a nightmare to navigate," he muttered. "The fog probably gets so thick you can barely breathe."

After more than two weeks of travel, he'd finally reached his destination.

"Alright. Time to meet Sakonji Urokodaki and prepare for the Final Selection." He started up the mountain path, his boots crunching against loose gravel.

Several hours of hiking later, Kaidō arrived at a modest wooden dwelling nestled among the trees. The house radiated a quiet, lived-in dignity—humble yet purposeful.

He approached the entrance and knocked firmly. "Hello? Is Sakonji Urokodaki home?"

Slide.

The door opened to reveal a man wearing a crimson tengu mask, his presence radiating the quiet authority of a master swordsman long past his prime but no less dangerous for it.

'So this is the former Water Hashira,' Kaidō thought, impressed despite himself.

'I've only seen him in the manga, but in person his aura is overwhelming. This is what decades of survival look like.'

"My name is Ryūjin Kaidō," Kaidō said aloud. "I'd like to participate in the Final Selection and join the Demon Slayer Corps."

Urokodaki regarded the young man before him with undisguised curiosity. The white hair accented with crimson, the delicate features, the elegant coat—everything about this stranger screamed unusual.

If not for his keen sense of smell confirming this was indeed a young man, Urokodaki would have sworn he was looking at a girl.

"How did you learn about the Demon Slayer Corps?"

"I..." Kaidō scratched the back of his head sheepishly.

'I can't exactly tell him I'm a transmigrator who watched the anime. He'd think I'm insane and throw me off the mountain.'

"Never mind," Urokodaki said after a moment. "I won't force you to answer. But let me ask you something else: If you encountered a demon, what would you do?"

Kaidō didn't hesitate.

"That depends on whether they've consumed human flesh. If I'm facing a man-eating demon—one that's murdered innocent people—I'd cut them down without a second thought."

His expression softened slightly.

"But if the demon was transformed against their will and has never harmed anyone? Then I'd let them live out a natural human lifespan and die peacefully when their time comes."

Urokodaki's head tilted fractionally—the only sign of his surprise. "Why would you think that way? And how would you determine which demons deserve mercy and which deserve death?"

"If we can't distinguish between monsters and victims, then we're no better than the demons themselves," Kaidō said quietly.

His voice carried a weight that seemed to age him beyond his years.

"Imagine someone who was turned into a demon through no fault of their own. They resist the hunger, never harm a soul, even dedicate themselves to helping people—but then a demon slayer discovers what they are and kills them on sight. How is that justice?"

He paused, letting the question hang in the air.

"Now imagine a human family that knowingly shelters a man-eating demon. They help it lure victims, dispose of bodies, profit from the carnage while innocent people die. Tell me, Master Urokodaki—what makes them different from the demons they serve?"

Silence descended like a heavy blanket.

Urokodaki said nothing. The question had no easy answer—perhaps no answer at all. Kaidō's logic was flawed in some ways, yet undeniably compelling in others.

Humans who collaborate with demons... do they deserve death? And demons who harm no one—should they be allowed to exist?

For the first time in years, Urokodaki found himself genuinely uncertain.

Finally, he spoke. "If you want to join the Demon Slayer Corps, you'll need to pass my test. Complete it, and I'll teach you everything I know. Now—follow me."

Without waiting for a response, Urokodaki turned and sprinted up the mountain with the fluid grace of a man half his age.

So it begins.

Kaidō activated Total Concentration Breathing: Constant and gave chase.

Urokodaki glanced back, expecting to see the young man struggling to keep pace. Instead, Kaidō was right behind him, breathing steady and controlled. "He's already mastered Constant? But where did he learn it?"

...

They reached the summit as the sun began its descent toward the horizon. Urokodaki turned to face his would-be student.

"Reach the house at the mountain's base before dawn. Do that, and you have my approval."

Before Kaidō could respond, Urokodaki vanished into the mist.

"Former Water Hashira indeed," Kaidō murmured, impressed. "Guess I'd better get serious."

He stretched his arms overhead, rolling his shoulders.

"The system gave me tools, but tools are useless if I don't know how to use them. Rewards mean nothing if I can't weave them into my fighting style through real training. The system won't hold my hand forever—if I die, I die."

His expression hardened into determination.

"Time to earn it."

He launched himself down the mountainside, senses heightened to maximum alertness as he dodged trap after trap—pitfall snares, tripwires, swinging logs, hidden spike pits.

What Kaidō didn't know was that Urokodaki had already decided to accept him the moment he'd articulated his philosophy about demons. Witnessing the Total Concentration Breathing had only cemented that decision.

But talent without discipline bred arrogance. Arrogance got you killed.

So Urokodaki hid in the canopy, watching as Kaidō navigated the gauntlet. The young man had every reason to coast on his natural advantages, yet he pushed himself relentlessly, treating the trial as if his life depended on it.

No complacency. No shortcuts. Just pure, stubborn determination!

"I approve of you, Ryūjin Kaidō," Urokodaki whispered to the wind before vanishing into the night.

...

Several hours later, the door to the mountain base house burst open.

Kaidō stood in the threshold, gasping for air, covered in leaves and dirt, his pristine coat torn in a dozen places. The journey had forced him to maintain Total Concentration Breathing while simultaneously dodging an absurd number of traps. Several times he'd been caught off guard, losing his breathing rhythm and having to restart, which wreaked havoc on his lungs.

But he'd made it.

"Huff... huff... Master Urokodaki... huff... did I pass?"

His breathing was ragged, uneven—but even as he spoke, Kaidō was already correcting it, forcing his diaphragm back into the proper rhythm. Within moments, his gasping had smoothed into something approaching normal, though still elevated.

"I approved of you hours ago, Kaidō," Urokodaki said simply.

Though his mask hid his expression, there was warmth in his voice. This young man could have taken the easy path, relied solely on his natural talent—but he'd chosen the hard road instead.

That spoke volumes.

"Really?? I passed!" Relief flooded through Kaidō—

GROWL.

His stomach chose that moment to voice its protest.

Kaidō's face flushed with embarrassment. "Uh..."

"Come. I've prepared fish stew. Eat, bathe, rest. Tomorrow, your real training begins." Urokodaki gestured toward the low table, already ladling soup into a bowl.

"Thank you, Master!" Kaidō settled cross-legged on the floor, accepting the offered meal. "I won't hold back!"

...

After dinner and a long, much-needed bath, Kaidō lay on the tatami mat, staring up at the ceiling.

His mind drifted through everything that had happened since his transmigration—the Kamado family's kindness, his encounter with Tamayo in Asakusa, and now Sakonji Urokodaki.

"It all feels like a dream... Like if I close my eyes and open them again, I'll wake up in my old bed. Mom will call me down for breakfast, Reika will complain about me sleeping in, and everything will be normal again."

But it wasn't a dream.

This was real. He'd truly crossed into another world.

"System," Kaidō whispered into the darkness. "Can I ever go back?"

[Ding! In response to Host's query: theoretically, yes. However—]

"Wait, WHAT??" Kaidō bolted upright, heart hammering. "I can go back?"

[Affirmative. However, there are conditions.]

The initial euphoria faded, replaced by cold pragmatism. "Of course there are. What's the catch?"

[Two requirements. First: Host must accumulate Interdimensional Energy.]

"Interdimensional Energy? What's that?"

[Interdimensional Energy powers the gateway between dimensions, allowing travel to specific times and locations across the multiverse.]

"Understood. And the second condition?"

[Host cannot return to their original world in their previous identity. Host has died in that timeline. Resurrection would disrupt causal order. Therefore, Host may only return with a different identity. Your memories will remain intact, and this system will handle all logistical arrangements.]

[Additionally: Host cannot return to a point in the timeline before their death. If two versions of Host's soul exist simultaneously in the same timeline, it will cause soul fragmentation or complete dissolution.]

"So I can't go back to the day before I died," Kaidō murmured, processing. "Two souls, one timeline, catastrophic results."

"But if I return the day after my death, my soul won't exist in that timeline anymore, so there's no risk of soul fragmentation or dissolution. The catch is I'd have to live under a different identity since I'm officially dead in that timeline."

[Correct, Host. Regarding resurrection, please remember: a timeline cannot support two identical souls simultaneously. Even this system has limitations in such matters.]

"Can I check how much Interdimensional Energy I currently have? And how do I earn more?"

[Ding! Searching... Search complete.]

[Current Interdimensional Energy: 0%]

[Acquisition Method: Complete system-issued quests to receive random Interdimensional Energy rewards. Minimum reward: 1%]

"So I can earn Interdimensional Energy from completing quests?"

[Affirmative. Each completed quest yields random Interdimensional Energy.]

"Got it. Looks like I'll need to travel around and trigger as many quests as possible to accumulate energy fast."

[Ding! Hidden Quest Detected.]

[Hidden Quest: Defeat Sakonji Urokodaki.]

[Success Reward: 5-10% Interdimensional Energy (Random)]

[Failure Penalty: None]

"Hell yeah!"

If he could beat Urokodaki tomorrow, he'd earn his first chunk of Interdimensional Energy. Once he hit one hundred percent, he could finally go home. Sure, he'd be wearing a stranger's face, but the chance to see his family again made it all worthwhile.

The Next Morning

Kaidō woke before dawn. Thanks to Total Concentration Breathing: Constant, the morning cold didn't bother him, and he felt completely refreshed despite the early hour.

After washing up, he headed straight to the training grounds. The moment Kaidō had stirred, Urokodaki had noticed.

"Up this early... he really is determined to get stronger," Urokodaki mused before heading to the kitchen to prepare breakfast.

...

"995, 996, 997, 998, 999, 1,000!!!"

"Phew—finally done with a thousand swings." Kaidō lowered the practice sword, rolling his shoulders. "Next time I should carve myself a proper wooden sword. This stick doesn't feel right."

"It seems you're ready for my special training." Urokodaki's voice came from behind him. "In that case—attack me with everything you have!"

"Understood, Master. Be careful!"

Kaidō raised the wooden practice sword over his shoulder, pointing the tip toward Urokodaki. Then he exploded forward—

WHOOSH.

THWACK.

Urokodaki blocked the strike one-handed, wood clashing against wood.

"Too slow!"

Another exchange. Another failure.

"Your attacks lack focus!"

Again.

"Still too slow!"

"You're raising your sword too high—too many openings!"

"Speed is better, but your strikes don't have enough power!"

Over and over, Kaidō attacked. Over and over, he hit the ground. But he didn't give up. Each failed exchange taught him something new—how Urokodaki moved, where the openings were, what worked and what didn't.

Combat experience could only be earned through actual combat. There was no shortcut.

His Total Concentration Breathing never faltered—inhale, exhale, inhale, exhale—a steady rhythm that kept his muscles oxygenated and his mind sharp.

This time, he incorporated everything he'd learned from the previous exchanges. He adjusted his grip, changed his approach angle, and launched another assault.

"Fast!"

Even Urokodaki was caught off guard. The boy had absorbed the lessons from their sparring and adapted his strategy mid-training. Impressive didn't begin to cover it.

Within moments, the tide turned. Kaidō's relentless barrage forced Urokodaki onto the defensive until—

CRACK.

Urokodaki wooden sword snapped in half.

Kaidō immediately stopped attacking, not because he'd won, but because his stamina had hit zero. His muscles screamed in protest, and his lungs burned despite the breathing technique keeping him upright.

If he'd had more energy, he would've kept going. The sparring session had revealed exactly where his weaknesses lay and how much he still needed to improve his real-world combat skills.

For the first time, he had a clear understanding of his actual fighting ability—not theoretical knowledge, but practical experience.

"You won." Urokodaki tossed aside the broken practice sword. "Tomorrow, come back here. I'll teach you every form of Water Breathing. How much you learn depends entirely on you."

What Urokodaki didn't say aloud: There's nothing more I can teach you after that.

"Finally... I actually won. If that had gone on much longer, I would've collapsed."

[Ding! Congratulations! Host has completed Hidden Quest.]