Demon Slayer: Dragon Hashira#36/37: Muzan's Downsizing, Tanjiro's Declaration, Tamayo's Letter, Genya's Request, Dragon Blood?

Infinity Castle

A demon resembling a middle-aged man with black hair and a beard, his face covered in cracks, stared around the labyrinthine Infinity Castle in confusion.

The kanji for Lower Two marked his left eye—Rokuro, Lower Rank Two.

Another demon, Lower Rank One, Enmu, had short black hair with red tips and two green strands, appearing perpetually sickly.

The kanji for Lower One was etched into his left eye.

Lower Ranks Three and Six had already been eliminated by Kaidō. Lower Four was turned into a card, severing contact with Muzan. Lower Five had been killed by Giyu. Only Lower One and Lower Two remained.

STRUM.

On a platform above, Nakime plucked her biwa. Instantly, both Lower Rank demons appeared before a woman wearing a black kimono adorned with floral patterns.

"KNEEL!"

The command came out in a man's voice. Both Lower Ranks collapsed to their knees, trembling violently.

'Lord Muzan!' Rokuro screamed internally. The figure before them was indeed Muzan, capable of taking any form.

"Rui is dead. He was Lower Five. And I have lost contact with Lower Four."

"I want to know why the Lower Ranks of the Twelve Kizuki are so pathetically weak??"

"Becoming one of the Twelve Kizuki is not the end—it is the beginning! Your purpose is to devour more humans, grow stronger, and serve me more effectively!"

"In the past century, the Upper Ranks have remained unchanged. But how many times have the Lower Ranks been replaced?? Only Upper Ranks eliminate Hashira. The Lower Ranks? Constantly replaced!!"

"Therefore, I have decided to disband the Lower Ranks. The Twelve Kizuki will consist solely of the Upper Ranks. That is sufficient." Muzan's tone left no room for argument.

"Now, do either of you have any last words?"

"N-no, my lord! I am still useful! I can still serve you! Please grant me more time—I promise I will prove valuable!" Rokuro pleaded desperately.

"How much time? What can you possibly accomplish?"

"Blood!! If you would grant me more of your blood, I will adapt to it! Then I can become a far more powerful demon and fight for you!!!"

"Why should I follow your instructions and give you blood?? Shameless creature—what makes you think you have any say??" Muzan snapped.

"No, my lord! I—I only meant—"

"SILENCE! Everything is my decision! My word is absolute! You have no right to refuse! What I declare 'correct' is correct! You dare give me orders? You deserve execution!"

SLASH.

Rokuro was consumed by Muzan's morphing right hand, devoured instantly. Muzan turned his gaze to Enmu. "Do you have any final words?"

Enmu raised his head, looking at Muzan with ecstatic adoration. "This is like a dream... having you personally execute us. Hearing another demon's dying screams... I feel so happy, so blessed!"

"What a wonderful sensation! I adore watching others suffer and despair—it is like a beautiful dream! Thank you for saving me for last," Enmu spoke with twisted rapture.

Muzan stared intently at Enmu, then injected his blood directly into the demon's body.

Thump-thump... thump-thump...

Enmu heard his own heart pounding violently as he writhed on the wooden floor.

"I see potential in you. I am sharing some of my blood."

"If you cannot adapt, you will die. But if you succeed—you will become stronger and serve me."

"Go kill a Hashira. If you can eliminate the long, white-haired Demon Slayer wearing a fox mask and wielding a greatsword, along with the hunter wearing hanafuda earrings, I will grant you even more blood!"

STRUM.

Nakime plucked her biwa. A sliding door appeared before Muzan. He stepped through, and it vanished behind him.

Another strum sent Enmu hurtling out of the Infinity Castle.

Enmu crashed into a dark alleyway, images of Kaidō and Tanjiro flashing through his mind.

"These are... Lord Muzan's memories... huff... like a dream! Hahaha! Kill the Hashira and those two boys, and I will receive even more of Lord Muzan's blood! This is absolutely magnificent!!"

————————————

Butterfly Mansion

Half a month into Tanjiro's recovery, he and Inosuke had started rehabilitation training. Every time they returned to the ward, however, they looked completely drained.

WHOOSH.

The door slid open. Tanjiro and Inosuke stood there, looking utterly depleted.

"Welcome back, Tanjiro, Inosuke," Zenitsu greeted from his bed. "What... what happened to you two?"

"Uh..." Both responded weakly, shuffling to their beds and pulling the covers over themselves.

"Sorry..." Tanjiro mumbled.

"Just... leave me alone..." Inosuke groaned.

"TELL ME WHAT HAPPENED! I start training tomorrow too!!" Zenitsu shrieked.

The Next Day

Zenitsu followed Tanjiro and Inosuke to the training grounds, muttering "This is terrifying" the entire way.

At the grounds, Aoi explained the regimen once more.

...

Flexibility exercises (handled by three younger girls) for those stiff from bed rest.

Reflex training (managed by Kanao Tsuyuri).

Full-body training (overseen by Aoi herself)—essentially tag.

...

"Any questions about the explanation?" Aoi asked.

"Sorry to interrupt, but I need a word with these two. You two—come with me!" Zenitsu demanded, pointing at Tanjiro and Inosuke.

"?" Tanjiro looked confused.

"Not going," Inosuke refused flatly.

"?(╬◣д◢)? I SAID GET OVER HERE!!" Zenitsu grabbed both by their collars and dragged them toward the exit. "Move it, you useless trash!"

Training Grounds – Back Courtyard

Zenitsu stood lecturing Tanjiro and Inosuke, even punching Inosuke once, accusing them of being in paradise while acting like they were in hell.

"What are you even talking about??" Tanjiro protested.

"SHUT UP, FOREHEAD BOY! Don't you realize this training means TOUCHING GIRLS?? Playing the teacup game lets you hold hands! Tag means you can HUG them!!"

"Every girl has two boobs, two butt cheeks, and two beautiful soft legs! When they pass by, they smell amazing! This is heaven! ABSOLUTE HEAVEN! WAAAHHH!!" Zenitsu grew increasingly worked up, leaping and spinning mid-air.

Inside the training hall, the girls heard everything. They felt... speechless.

Zenitsu joined the training afterward, clearly savoring every moment—until the final full-body session when he hugged Aoi and got beaten severely.

Bruised and battered, Zenitsu muttered: "Won the battle... lost the war..."

————————————

Two Months Later

'System, monthly check-in,' Kaidō mentally commanded.

[Ding! Check-in successful!]

[Reward: Isolation Barrier]

[Isolation Barrier: Blocks all external connections, including Muzan Kibutsuji's link to demons.]

"Isolation Barrier—not bad. Combined with last month's Life-Saving Talisman, these are solid rewards!"

[Life-Saving Talisman: When carried, negates one instance of fatal damage.]

"Haven't been back to Headquarters in two months. Time to return and clear out some demons." Kaidō flew toward Corps Headquarters on his greatsword, hunting demons along the way. The demons never expected him to backtrack—they barely emerged from hiding before losing their heads.

Arriving at Headquarters, Kaidō headed to the Butterfly Mansion's training grounds to check on Tanjiro and the others. En route, he encountered Hotaru Haganezuka and Tecchin Tecchikawahara.

'Must be delivering blades to Tanjiro and Inosuke.' Approaching, Kaidō greeted them.

"Haganezuka-san! Long time no see! How are—uh... what's wrong?" Something felt off—Haganezuka radiated murderous intent.

"I am here to deliver Tanjiro's sword!" Haganezuka declared stiffly.

"Ah, okay, understood!" Kaidō replied, mentally offering Tanjiro three seconds of silence.

"Let me see your greatsword!" Haganezuka commanded.

"Uh... sure..." Kaidō drew his greatsword and handed it over.

Haganezuka examined it meticulously. No damage—exactly as pristine as when first forged.

"Excellent! Hahaha! You have taken great care of the weapon I forged! Unlike that guy..."

Right on cue, Tanjiro and Inosuke appeared in the distance. Speak of the devil.

Seeing Tanjiro, Haganezuka returned the greatsword, handed his belongings to Tecchin, then drew a kitchen knife from his kimono.

"Haganezuka-san! Long time no see! You're looking gre—AHHHHH!!" Before Tanjiro could finish, he saw Haganezuka charging with murderous intent and barely dodged.

"Haganezuka-san—"

"YOU BROKE MY SWORD! YOU ACTUALLY BROKE MY SWORD!"

"I'm sorry! But I was about to die! The enemy was incredibly powerful...!!"

"Wrong! It is your fault my blade broke! None of that matters! If not for you, my sword would not have broken!!" Haganezuka jabbed Tanjiro's face repeatedly with his finger.

"I'LL KILL YOU!"

"I'm sorry! I'm so sorry! Someone help! Kaidō-san, save me!"

"Sorry, Tanjiro—you're on your own here!" Kaidō shrugged helplessly.

And so, Tanjiro was chased by the knife-wielding swordsmith for a solid hour...

Meanwhile, Kaidō sat atop the Butterfly Mansion's wall, munching an apple, watching Tanjiro get "hunted" around the estate.

"Now that's an iconic scene. How do they keep this up?? One runs, the other chases." He took another bite and kept watching.

————————————

Back at his estate, Kaidō reviewed the timeline.

"One month until the Mugen Train arc. I need to use this time to prepare!"

"Akaza—I will defeat you! Even if I cannot beat you, I will fight with everything I have to protect everyone, including Kyojuro Rengoku! I absolutely refuse to let that tragedy happen!!" His resolve hardened.

In his previous life, watching Kyojuro die at Akaza's hands had affected him deeply. He had wished he could enter the Demon Slayer world and fight alongside Kyojuro to save him.

That wish had come true—though his method of arrival was rather absurd. Getting hit by a delivery truck made him wonder if those drivers were specifically assigned by the anime multiverse for isekai purposes.

Compared to others, his death wasn't so bad. Some died from staying up too late, others from... unusual bodily functions, lightning strikes, choking on water. The list went on. Every bizarre death imaginable seemed to lead to isekai—some even more ridiculous, like being scared to death...

"Life really is unpredictable..." Kaidō muttered self-deprecatingly.

<><><><><><><><>

Kaidō stood in his estate's courtyard, training intensely. A Kakushi member approached, carrying an envelope.

"Dragon Hashira-sama, a letter has arrived for you!"

Kaidō lowered his greatsword. "Thank you for bringing it!"

"Not at all—serving a Hashira is my honor." The Kakushi bowed and departed.

Returning inside, Kaidō opened the envelope. The sender was Lady Tamayo:

————————————

Kaidō-kun,

Thank you for sending the blood samples from the Twelve Kizuki, especially from an Upper Rank. My research has progressed considerably because of your assistance.

I have heard about your achievements—becoming a Hashira in less than a month, slaying an Upper Rank demon. The Upper Ranks possess fearsome power, yet you defeated one.

I can sense it now—Muzan Kibutsuji's fate is sealed. You will be the one to end him. Thank you, little Kaidō-kun.

—Tamayo

————————————

Kaidō set the letter down and sighed heavily.

"Why does everyone keep calling me 'little'? Shinobu, Mitsuri, Kanae constantly... Now even Lady Tamayo!" He rubbed his temples. "I just want to know where exactly I am 'little'... Okay fine, I am pretty small right now. (╥╥)"

His current appearance was entirely the system's fault. Speaking of which—

[Host, I am perfectly respectable!] The system's feminine voice echoed, sounding slightly offended.

'Respectable? Then explain who designed this body? Who picked these clothes? What about that kimono reward? And why does the Mukago Collection Card look like that?'

[Please rest assured, Host—everything is completely normal! This system has absolutely zero interest in seeing you in women's clothing!]

'I swear to—' Kaidō cut off the thought. 'Whatever. Not worth it.'

A shout from the courtyard interrupted him.

"Excuse me! Is the Dragon Hashira here?"

Kaidō stepped outside, recognizing the voice instantly. Sanemi Shinazugawa's younger brother stood at the entrance—Genya Shinazugawa. Dark mohawk-style hair, a scar running across his nose from his right cheek—a reminder of the night his demon mother attacked him.

Poor physical conditioning prevented him from using Breathing techniques. However, his unique jaw strength and digestive system allowed him to consume demon flesh and temporarily gain demonic abilities. The stronger the demon, the greater his power boost. A rare case in the Corps. His inability to master standard techniques frustrated him. Being a teenager, he was awkward around girls, blushing instantly. But around Sanemi, guilt turned him into a nervous wreck.

"You're Genya Shinazugawa, right? What brings you here?"

Genya dropped to his knees, forehead touching the ground. "Dragon Hashira-sama! Please make me stronger!"

Genya admired strength and had heard stories about the Dragon Hashira. If Kaidō trained him, maybe he could finally fight alongside his brother.

Kaidō knew Genya's motivation but asked anyway. "Why do you want to become stronger? Tell me."

"I... I..."

Kaidō's expression softened. "It's to prove yourself to your brother, isn't it?"

"Y-yes." Genya's voice was barely a whisper.

"First, tell me what you are capable of."

"I cannot use Breathing techniques. But my body is... different. I have powerful jaw strength and a unique digestive system. I can devour demons and temporarily gain their abilities. The stronger the demon, the stronger I become!"

Kaidō stroked his chin thoughtfully. An idea formed.

"I can teach you Breathing techniques. Whether you master them depends on your effort."

"But I have tried learning before! It didn't work—"

"I have a method worth trying. If it fails, I will teach you something else."

He retrieved a Breathing Affinity Pill from his inventory—a previous reward. He'd used one himself, allowing Water Breathing to integrate seamlessly. Whether it would work for Genya was uncertain.

"Swallow this pill. Let's see what happens."

Genya took the pill without hesitation and swallowed it. Within moments, searing pain erupted in his lungs. He collapsed, writhing.

'System! What is happening??'

[This is normal, Host. The Breathing Affinity Pill is restructuring his pulmonary system.]

'He is not going to die, is he??'

[Absolutely not. The process is safe.]

Relieved, Kaidō crouched beside him. "Genya! Hold on—this is normal! The pill is rebuilding your lungs so you can learn Breathing techniques!"

"Yes! I will... I will endure it! I have to prove myself to my brother!" Genya's determination burned through the pain.

The transformation lasted about ten minutes before subsiding.

"How do you feel?" Kaidō asked.

"My lungs... feel incredibly clear. Like I can breathe deeper than ever," Genya replied, taking several experimental breaths, eyes wide.

"Perfect. Now I will teach you Water Breathing. Mastery is up to you."

"Yes, Dragon Hashira-sama!"

————————————

Three Days Later

Genya had barely grasped Water Breathing's fundamentals. His technique was rough but functional.

"Genya, you have achieved basic proficiency. But you are nowhere near combat-ready. You need extensive practice."

Kaidō placed a hand on his shoulder. "Once you have fully mastered it, find me again. Then I will teach you all the Forms."

"Yes! Thank you, Dragon Hashira-sama!"

Suddenly, a vicious gust erupted from behind—an attack aimed at Genya.

Kaidō spun instantly, intercepting the strike. "Sanemi! Are you insane?? Trying to kill your own brother??"

The attacker was indeed Sanemi, sword drawn, radiating killing intent.

"Get out of my way!" Sanemi snarled.

"Big brother..." Genya trembled.

"SHUT UP! Do not act familiar—I don't have a brother! Keep this up and I will gut you myself!" Sanemi's words were venomous.

"Enough, Sanemi! You can protect him today, but not forever!" Genuine anger flashed across Kaidō's face for the first time. He understood Sanemi's intent—driving Genya away for his safety—but the method was too cruel.

"What the hell are you implying?? I am not protecting anyone! He cannot even learn basic Breathing—clearly talentless! Worthless trash like him doesn't belong here!"

"But i..." Genya's voice broke. "I-I ate demons..."

"YOU WHAT?? YOU ATE DEMONS??" Sanemi's fury exploded. His hand shot forward, fingers aimed at Genya's eyes, intending to blind him.

Kaidō lunged, catching Sanemi's wrist. 'This is bad! The confrontation happened early because of me! Butterfly effect!'

"Sanemi," Kaidō's voice dropped seriously. "I need to tell you something. Using my family's secret technique, I glimpsed fragments of the future concerning Genya."

"Tch! Fine. What did you see?" Sanemi's rage cooled slightly, needing to know.

"Genya, there is something both of you need to understand. Before I explain, let me show you."

Kaidō activated Demonic Eye, pulling Genya into an illusion recreating their family's tragic past—memories from the manga. The truth behind Sanemi's harshness.

Genya's body went rigid, then collapsed.

"What happened??" Sanemi's concern overrode his anger.

"He is fine. I am showing him the truth," Kaidō said gravely. "Now, about Genya's future." He met Sanemi's eyes. "Your brother will die protecting you."

"WHAT?? Are you kidding?? You think that joke—"

"Was reviving Kanae a joke?"

Sanemi froze, silenced.

"I know you verbally abuse him to drive him away. You want him to live normally—get married, have kids, grow old," Kaidō said gently but firmly. "But if he leaves and you die... do you think he will be okay? You are his only family. Will he be happy without you?"

The words struck home. Sanemi remained silent.

"Also, your brother has learned Breathing techniques now. I taught him."

"??"

"People cannot stand still forever, Sanemi. Do not let your little brother surpass you." Kaidō clapped his shoulder, then stepped back.

Understanding dawned in Sanemi's eyes. If he didn't grow stronger, Genya might surpass him. The protector could become the protected. Unrealistic, maybe, but possible. Only by becoming stronger could he truly protect Genya.

"I understand. Thank you, Kaidō." The gratitude was genuine.

"We are comrades. No need for thanks."

Genya stirred and stood immediately, walking toward Sanemi.

"Big brother, I am sorry! I misunderstood you! You were trying to protect me, but I—I said those terrible things!" Tears streamed down his face. He turned to Kaidō. "Thank you, Dragon Hashira-sama. For everything."

"Now that things are cleared up, you two probably need to talk. I will give you privacy," Kaidō smiled. "Genya, keep training Water Breathing. Find me once you have mastered it."

He turned and left.

————————————

[Ding! Congratulations! Hidden Quest Complete!]

[Hidden Quest: Brotherhood]

[Reward: Dragon Blood]

[Dragon Blood: Contains immense draconic power. Strengthens physical capabilities to peak human condition. Small chance of evolving into a Dragon-Human Hybrid.]

"Holy—" Kaidō nearly shouted. "Are you serious??" His mind raced. 'If this pushes my body to its peak, I will have a real shot at defeating Upper Rank Three. Kyojuro can survive!'

Fierce determination filled him. "I will use it tonight. Right now, I have something else to handle."