The day of the demonstration arrived.
Most of the Swordsmith Village had gathered in the wide forest clearing, murmuring with anticipation as they waited for the unveiling of Akira's new prototype, his upgraded Yoriichi Type Zero.
The normally quiet village suddenly felt alive.
Tanjiro hurried toward the clearing, with Nezuko in the box, his eyes bright with excitement.
He and Nezuko had helped Akira test the prototype during the early stages, so he was eager to see the final form.
But he also had… concerns.
"I hope everything goes alright… Akira-san's machine… I really hope it works well this time. It would be bad if it explodes again… or starts attacking people randomly like last time, again." He muttered.
Yes, emphasis on again.
Akira's machine did not work perfectly from the start.
There was that time it exploded for no apparent reason. No fire, no smoke, just a sudden burst that made everyone's hair stand straight up like porcupines thanks to some freak static discharge. And then there were the other tests… where the prototype suddenly activated and started chasing everyone around the village.
Including Haganezuka.
Especially Haganezuka, for twenty minutes straight.
Good thing nobody was seriously injured. As for whether Akira caused those incidents by accident or if he simply thought it would be funny, no one truly knew.
Tanjiro sighed, wiping nervous sweat from his forehead.
"Akira-san… please… just let it work normally this time…"
As Tanjiro recalled all those disasters with a tired smile, he noticed commotion up ahead.
Kotetsu was clutching a wooden box wrapped tightly in cloth, while someone stood before him, questioning him with a cold, detached tone.
Tanjiro recognized him instantly.
The Mist Hashira, Tokito Muichiro.
"What's inside? It's giving off heat," Muichiro said flatly.
"Open it."
Kotetsu panicked and hugged the box tighter.
"I-It's important! Akira-san told me to bring it quickly! I can't show it to anyone!"
Muichiro's expression didn't flicker in the slightest.
"Important? That doesn't matter." His voice was calm, almost airy. "I asked you a question earlier, and you didn't answer. I'm going to take it from you."
He raised his hand, not for a deadly strike, just a light hit to force Kotetsu to drop the box.
But before his hand could land.
CLACK.
Tanjiro grabbed Muichiro's wrist.
"Please stop! How can you treat a child like that?!"
Muichiro blinked at him.
"You're noisy. And your voice is annoying. Who are you?"
"It doesn't matter who I am! You're trying to hit a kid and take something that isn't yours! That's stealing!"
Muichiro calmly replied, "I am not stealing. I am inspecting a dangerous object. He is not cooperating."
Kotetsu shook his head rapidly.
"This is something Akira-san asked me to bring! He said not to open it…it's really important!"
Muichiro dismissed that.
"I don't care. You are obstructing a Hashira in his duty. A Hashira's time is worth far more than time spent by you people."
"That's not true!" Tanjiro argued.
"And he's following Akira-san's orders! You're the one obstructing him!"
Muichiro stared at Tanjiro, confused. "Why do you involve yourself in this? Why do you care about other people?"
Tanjiro answered without hesitation.
"There's nothing wrong with helping others. Whatever you do for others comes back to help you, too!"
Muichiro's blank expression twitched, surprise flickering in his eyes.
But before he could speak.
A booming, warm voice cut through the air like sunlight blasting through morning fog.
"OHO! Tokito! There you are! Ah, Tanjiro is here too!"
All three of them turned as Rengoku Kyojuro strode toward them, his steps thunderous, his presence blazing like a bonfire in human form. His smile was as bright as ever.
"Excellent! I see your spirits burn brightly this morning!"
Tanjiro's face lit up. "Rengoku-san!"
After the Mugen Train incident, Tanjiro held deep respect for him, almost like an older brother. Rengoku gladly returned that warmth.
Muichiro didn't turn fully, but he responded in his usual detached tone,
"…Rengoku."
Rengoku surveyed the tense standoff for only a moment before his sharp eyes fell on the cloth-wrapped wooden box clutched tightly in Kotetsu's arms.
"Is that the item Akira requested?" He asked with genuine curiosity. "The Solar Core?"
Kotetsu nodded so quickly it was almost a blur.
"Yes! Akira-san asked me to bring it quickly!"
Muichiro blinked. "…Solar… core?"
Rengoku placed a reassuring hand on Muichiro's shoulder.
"There is no need for concern, Tokito." He said calmly. "Akira will explain its purpose during the demonstration. Let the boy pass. Everyone is waiting."
Muichiro silently thought it over… then let his hand fall to his side.
"…Alright."
Kotetsu and Tanjiro both exhaled in relief.
Rengoku clapped his hands together, flames of enthusiasm practically bursting from his smile.
"Excellent! Then let us go together. Everyone is eagerly awaiting the demonstration! Come, let us hurry!"
So they all returned to the clearing where the demonstration was taking place. A large crowd had already gathered, villagers, swordsmiths, the village chief, and several important elders from the hidden smithing community.
Standing among them were two Hashira: Kanroji Mitsuri, waving excitedly, and Kocho Shinobu, watching with a polite but slightly wary smile.
Near the front stood Lady Ubuyashiki Amane, graceful as always, accompanied by two of her daughters. They had come to represent Kagaya, who was too ill to attend.
And Akira and Erika stood beside a massive shape hidden beneath a large cloth.
Tanjiro and Kotetsu rushed up to them, just in time to hear Erika scolding, "I can't believe you forgot something that important!"
Akira had a nervous smile as he adjusted something behind the sheet. "I'm sorry! I just… got too focused on making it look cool, okay? But, oh look, they're here!"
Kotetsu hurried forward and thrust the cloth-wrapped box into Akira's hands.
"Akira-san! I brought it!"
Akira smiled gently. "Thank you, Kotetsu."
Kotetsu puffed his chest proudly. "Don't worry about it!"
Tanjiro eyed the box curiously. "Akira-san, what is that?"
Akira lifted the lid and revealed a small metallic sphere inside.
"Oh, this? This is just the core of the solar reactor I made."
He pressed a button on the machine beneath the sheet. A hidden compartment snapped open with a mechanical click, and a cylindrical chamber slid out.
With practiced precision, Akira placed the sphere inside, sealed the cylinder, and slid it back into the machine.
Then he turned toward the gathered crowd, brushing off his hands.
"Alright, everyone, we're ready."
Akira stepped forward, lifted his hand dramatically, and announced:
"Now… let me introduce you to my latest creation, Yoriichi Type Null."
With a single tug, he ripped the sheet away.
A collective gasp rippled through the crowd.
Standing beneath the cloth was a towering seven-foot metal giant, a hulking machine with six arms, each gripping a wooden sword. Its body was made entirely of polished metal, its torso reinforced with layered plating, and its six limbs gleaming under the sunlight.
Its glowing red eyes lit up as it activated and stepped forward, and walked to the center of the clearing on its own.
The spectators froze in disbelief.
Rengoku's eyes burst into flames of excitement.
"HOH! MARVELOUS! A BRILLIANT WARRIOR OF METAL!!"
Shinobu's eyebrow twitched. "It looks more like a monster than the original Yoriichi Type Zero…"
Mitsuri beamed. "It's so big! I bet it's super strong!"
Lady Amane Ubuyashiki gave Akira a gentle nod.
"Please begin, Hoshino Akira. The Mist Hashira Tokito Muichiro will be its opponent."
The Mist Hashira stepped forward, wooden sword in hand. His blank, serene expression did not change, even as he stared at the mechanical giant.
"I still don't understand the point of this," he said calmly. "A doll cannot surpass a Hashira."
Akira grinned. "Well… challenge accepted. Null, show him what you're made of."
The machine responded with a low, mechanical growl, almost like an acknowledgment.
Rengoku raised his arm. "I will referee this match! Only wooden swords will be used! Now—BEGIN!"
CLANG—!!
Type Null's six arms unfolded like a mechanical lotus blooming open.
CLICK—CLICK—CLICK
The wooden swords rotated into formation, each poised like a hunting predator.
Muichiro vanished.
"Mist Breathing, First Form—Low Clouds, Distant Haze."
He reappeared behind Type Null, blade flashing toward its neck.
CLANG!!!
Blocked.
Without even turning, the machine used two arms to intercept the strike from above. Two more parried the lower cut. The remaining pair stabbed forward with mechanical precision.
Muichiro flipped away effortlessly, landing light as mist.
His eyes narrowed.
"…It reacted instantly."
Akira smirked.
"It sees in all directions. It doesn't need to predict your movements, it always knows where you are."
Muichiro's eyes sharpened as he rushed again.
"Mist Breathing, Second Form—Eight-Layered Mist!"
Eight slashes tore through the air.
CLANG! CLANG! CLANG! CLANG!
Six arms blurred like a storm of steel.
Every slash was blocked.
But Muichiro didn't stop. He accelerated, becoming a streak of mist circling the machine.
Still, Type Null's arms moved with perfect synchronization.
CLANG! CLANG! CLANG!
Rengoku leaned forward, astonished.
"Splendid!! To keep pace with a Hashira!!"
Even Shinobu's eyes widened.
"Such reaction speed… It's almost unfair to fight a machine like this."
Muichiro's form almost looked like it dissolved into swirling fog, as he sped up.
"Mist Breathing, Sixth Form—Lunar Dispersing Mist!"
He launched into the air and rained down countless slashes, finishing with a spiraling vertical strike.
But Type Null blocked everything and then counterattacked instantly.
Muichiro barely parried, his eyes widened.
"It predicted my movement…"
Type Null advanced, and this time, its motions resembled Muichiro's own techniques.
Muichiro muttered, stunned,
"…It learned my moves."
Akira proudly folded his arms.
"Yup! It can learn its opponent's techniques mid-fight and adapt on the spot. It's a learning computer."
Muichiro steadied his stance, eyes sharpening.
"Mist Breathing—Fifth Form: Sea of Clouds and Haze."
He vanished into a blur.
His movements zig-zagged at blistering speeds, slashing around Type Null in a spiraling assault. A barrage of cuts rained from every angle.
CLANG–CLANG–CLANG–CLANG!
Type Null blocked each strike with its six synchronized arms, but Muichiro was ramping up.
He muttered under his breath,
"Mist Breathing, Second Form: Eight-Layered Mist."
Eight rapid-fire slashes carved through the air again, but this time, Muichiro's increased speed made it look like Type Null was barely keeping up.
A few even slashes slipped through its guard.
Muichiro exhaled, gathering power for his finishing move.
But.
Yoriichi Type Null suddenly froze.
Then.
Its six arms snapped into a new formation.
A stance no one had ever seen before.
And then it spun.
FAST.
EXTREMELY FAST.
Like a demonic wind turbine.
Like a murderous Beyblade unleashed upon the world.
WHRRRRRRRRRRRRRRRR!!!
Muichiro's eyes went wide, for the first time in this entire fight.
"W-What…?"
BONK!!!
A single wooden sword smacked him directly on the forehead with the divine precision of a cosmic slap.
Muichiro flew backward, rolling across the dirt like a rag doll.
The spinning slowly stopped.
The clearing fell into complete silence.
The machine stopped spinning.
Everyone fell silent.
Then.
Muichiro's eyes widened again. Then trembled. Then filled with tears.
"…Yuichiro… brother…?...I… I remember…"
Lady Amane gasped softly. "No way… His memories returned."
Shinobu blinked hard. "Is that… even possible?"
Rengoku pointed dramatically. "A STRIKE SO POWERFUL IT HEALS THE SOUL! AMAZING!!"
Everyone was frozen in shock.
Even Akira.
Especially Akira.
Selena's telepathic voice chimed in, half-laughing, "Brother… did you plan this?"
Akira replied instantly, horrified, "Of course not! Even I'm not insane enough to cure amnesia by blunt force trauma!"
He had been thinking of ways to help Muichiro recover his memories…
But this was not on the list.
Shinobu rushed forward.
"He needs medical attention!"
And a few Demon Slayers carefully lifted Muichiro and rushed him away. Shinobu followed right behind them.
Rengoku finally declared.
"THE WINNER, YORIICHI TYPE NULL!!"
The clearing burst into cheers.
Lady Amane stepped forward.
"Hoshino Akira… your creation has proven its ability."
Her eyes drifted briefly toward Muichiro, who was still softly crying as he was carried away.
"Perhaps… too effectively," she added, her voice calm but subtly shaken.
The village chief trembled. "Yes… terrifying indeed…"
Rengoku slammed his fist into his palm. "I APPROVE IT! EXCELLENT! A MACHINE WORTHY OF THE DEMON SLAYER CORPS!"
Mitsuri nodded. "As terrifying as it looks… It's wonderful!"
And just like that, Yoriichi-Type Null was officially accepted.
Even though its first recorded achievement was accidentally curing a Hashira's amnesia with a wooden bonk.
Preparations immediately began to produce more of them.
The Ubuyashiki family poured their full support and resources into the project, after all, this machine could save countless lives and perhaps even stand against Muzan and the Upper Moons.
Production started.
Two months passed.
Akira tirelessly crafted every core and CPU himself, since no one else could make them.
The swordsmiths handled the other parts, hammering away day and night.
But even with everyone working at full force…
They only managed to build ten units.
Mostly because Akira couldn't resist adding upgrades along the way.
Like Wisteria poison dart launchers, Wisteria poison coating on the blades, and of course, solar energy charging, giving the swords devastating power.
In truth, Type Null didn't need the poison.
Its solar-charged blades alone made it a perfect demon-killing machine.
The days passed peacefully.
But Akira knew it wouldn't last.
He knew the next battle was getting closer.
And indeed…
Deep within the shadows, a certain pottery demon had already discovered the hidden village.
The peace was about to end.