In the Demon Slayer world.
On April 27th, Taishō Year 3, this became the most unforgettable day in Ubuyashiki Kagaya's fifteen-year tenure as head of the Ubuyashiki clan and commander of the Demon Slayer Corps.
It was also the day that, for Kibutsuji Muzan, after a thousand long years building up his Six Upper Moons, nearly three of them were wiped out in one go—a day of bitter humiliation.
Aside from Upper Moon One (Kokushibō), Upper Moon Two (Dōma), and Upper Moon Six (Gyūtarō, rescued just in time by Dōma), the rest—Upper Moon Three Akaza, Upper Moon Four Hantengu, and Upper Moon Five Gyokko—all died.
And the man at the center of the storm—the main cause of the sudden shift in the balance between Demons and the Demon Slayer Corps—was none other than Kamado Roy.
On April 28th, under a canopy of dense wisteria, a hidden village lay nestled in the trees. At its heart, a manor—ancestral home of the Ubuyashiki family for nearly a thousand years.
"Caw—caw—"
Messenger crows circled overhead while the Pillars who had gone out on missions returned one after another. Seven had departed. Now, seven came back—but one of them returned missing an arm.
That was the ever-"flashy" Sound Pillar, Uzui Tengen.
"What a damn shame. If that bastard hadn't run, I definitely would've killed him!"
Uzui's left arm was gone clean at the shoulder. The more he thought about it, the more irritated he got.
Back in the Entertainment District, when they confronted that demon sibling pair, he'd already cracked their attack patterns using Sound Breathing and had begun to turn the tide. He was sure he could've overpowered them.
Then a metal fan appeared out of nowhere, blocked both him and Sanemi at once, helping the demon siblings escape.
Worse—he'd had to sacrifice his left arm, frozen solid and shattered, just to break free of the ice and flee with Sanemi.
"Dōma. Upper Moon Two. I swear—next time I see him, I will kill him."
Beside him, Shinazugawa Sanemi scowled even harder than Uzui.
He couldn't forget the way Dōma had looked at them—flicking his fan, recognizing who they were, and then sighing in disappointment.
"Tch. Not the main one. What a waste."
He hadn't even seen them as worth the trouble—coming only for the "real target."
Sanemi didn't want to think about who that "real target" was. But that hundred-meter flaming blade that had skimmed past his shoulder, splitting a courtyard in half—that image had been looping through his mind for days on end.
He clenched his teeth and sulked in silence.
The Water Pillar, Tomioka Giyū, and the Serpent Pillar, Iguro Obanai, stayed quiet as well. One perched in a tree, the other sitting alone in a corner.
Their mood was even darker than Sanemi's.
Because unlike the others—they hadn't encounted any Upper Moons. Not even a Lower Moon.
In the three cases Ubuyashiki Kagaya had initially suspected were bait set by Muzan to lure Roy out—
Roy's Infinite Train,
Uzui & Sanemi's Yoshiwara Entertainment District, and
Rengoku's Swordsmith Village mission with Kanroji Mitsuri and newcomer Tokitō Muichirō—
Every team had run into Upper Moons.
Worse still—Rengoku's team not only met them, they killed them.
After Roy cut down Akaza, Rengoku's group went on to kill two more—Upper Moon Four Hantengu and Upper Moon Five Gyokko—all in one campaign.
Their names had become the talk of the Corps.
"Mitsuri-sama, you're amazing!"
"Are Upper Moons really that scary? I heard every one of them looks like some nightmare beast—is that true?"
In a corner of the courtyard, a few Kakushi who were close to Kanroji Mitsuri crowded around her, eyes sparkling.
Fortunately, Mitsuri had a good temper, bright and open-hearted, heavily influenced by Rengoku's warmth. Everyone loved her—otherwise…
Well, if Iguro had seen it wrong, he'd have already dropped from that tree in a jealous rage.
"W-well, it was all thanks to my teacher, really," Mitsuri waved her hands frantically. "It was Sensei who killed them."
"Both Upper Moons?"
"Both."
Silence.
The courtyard fell still.
Every gaze shifted toward the young man standing tall as always, waiting for the Pillar meeting to begin.
Rengoku Kyojūrō.
Yellow hair flaring like flames, the ends dyed red.
He stood as he always did—chest out, posture proud—but something about him felt different now.
He was heavier, somehow. Vast.
Like the sun overhead—once it rose, once it tore apart the darkness, no one could ignore it. Not even demons.
"What exactly happened back there?" someone whispered to Mitsuri, eyes sneaking toward Rengoku.
Muichirō had been with him at the Swordsmith Village, and Tengen had taken notice of the boy's changed demeanor.
"Muichirō. You saw it, didn't you?" Uzui asked, slinging his only remaining arm around the boy's shoulders.
Muichirō's usual vacant eyes, hollow from lost memories, brightened faintly.
He glanced at Rengoku.
"…He was strong," he said.
"Details," Uzui insisted.
Muichirō frowned slightly, searching for words.
"Strong enough that… it wasn't just one person," he said quietly.
The effect was immediate.
Sanemi, Iguro, Shinobu, even Giyū—all turned their attention toward Rengoku.
And just then—
Clap.
A clean slap echoed.
Sitting at the main veranda, beads rolling through his fingers, the Stone Pillar Himejima Gyōmei pressed his palms together and chanted softly,
"Namu Amida Butsu.
Quiet. The Lord has arrived."
He glanced toward Rengoku as he said it, then dropped to one knee, bowing.
From inside the residence, supported by his wife Amane and their daughters, Ubuyashiki Kagaya slowly stepped into view.
"Lord!"
Shinazugawa Sanemi, Uzui Tengen, Kochō Shinobu, Iguro Obanai, Kanroji Mitsuri, Tokitō Muichirō, and Tomioka Giyū all knelt in unison.
One person did not.
Which made him stand out even more starkly than Tomioka once had.
Not Roy—he wasn't here.
It was Rengoku Kyojūrō.
He remained standing.
He didn't kneel.
He simply bowed his head slightly when Ubuyashiki appeared.
The reaction was instantaneous.
Even the Kakushi standing in the shadows stared, eyes wide.
"Kyojūrō! Do you have any idea what you're doing?"
Sanemi exploded.
Roy not kneeling had been… tolerable. Roy didn't belong to the Corps, after all, and owed them nothing.
But Rengoku?
"You're a Pillar!" he shouted. "Act like one!"
Even Shinobu and Obanai, who were usually prickly and sharp-tongued, said nothing—but their expressions were far from calm.
Plainly put:
This wasn't like Kyojūrō.
This wasn't the big-brother figure who always smiled, always shouldered burdens, always looked after everyone.
This was… something else.
A small part of Giyū, watching from the rightmost position at the back, felt a strange déjà vu.
He'd seen someone do this before.
Someone who also refused to kneel, who'd only inclined his head slightly when Kagaya appeared.
His junior.
Kamado Roy.
"Namu Amida Butsu. Kyojūrō, I think you owe Ubuyashiki-sama—and all of us—an explanation," Gyōmei said quietly, beads sliding through his fingers.
His tone wasn't harsh, but the weight behind it was crushing.
"Gyōmei," Kagaya raised a hand gently.
He smiled, pale face as warm as ever, and asked,
"Kyojūrō. I heard that Sir Shinjurō has quit drinking?"
Rengoku took a deep breath.
"I was just about to report that, Lord," he said loudly. "Father is preparing to return. He'll be coming to see you soon."
Gyōmei's fingers stilled, tears streaming freely down his cheeks again as he murmured another sutra.
The others—Uzui, Shinobu—exchanged looks.
Even Sanemi, anger momentarily displaced, frowned in surprise.
If anyone could be called the "oldest line" in the Demon Slayer Corps, the Rengoku family would claim that title. Generations of Flame Pillars…
Everyone knew how far Shinjurō had fallen—drowning himself in alcohol and bitterness, lashing out at everyone, including Kyojūrō.
And yet now… he'd sobered up and planned to return?
Even Ubuyashiki looked visibly taken aback, holding that information in his mind like a precious jewel.
"That is good news," he said warmly. "Sir Shinjurō is a legend. If he wishes to return, all he need do is say the word and I will see it done."
"Thank you, my lord," Kyojūrō said, bowing deeply. "But I must ask for your forgiveness for my discourtesy just now."
He straightened, golden eyes burning with resolve.
"A servant cannot serve two masters. I am here today to resign the title of Flame Pillar. From here on, I will no longer hold office in the Demon Slayer Corps."
The air vanished from the room.
"Clang—!"
Sanemi's blade flashed free of its sheath.
"You've gone too far, Rengoku Kyojūrō!"
"Wind Breathing, First Form: Dust Whirlwind Cutter!"
A tornado roared to life, laced with slicing wind blades, streaking straight for Kyojūrō's face.
And then—
Flame blossomed.
A blinding arc of fire cut across the air.
In the same instant, Kyojūrō sheathed his sword as if he had done nothing at all.
The roaring wind vanished—chopped apart and burned to ash mid-spin.
Everyone stared.
Sanemi stood frozen, grip tight on his sword.
The others—Iguro, Shinobu, even Mitsuri—watched in stunned silence.
The slash had been so fast, so sharp, so hot that most of them had barely registered it.
That wasn't just "strong."
That was different.
This wasn't the same Rengoku they thought they knew.
Muichirō's eyes flickered as he remembered the Swordsmith Village: Rengoku alone chasing Gyokko and Hantengu down and cutting them to pieces.
He'd thought it strange then. Now…
It felt inevitable.
A huge hand settled on his shoulder.
Muichirō glanced over to see Uzui, gaze fixed on Kyojūrō.
"You were right," Uzui said quietly. "That kind of flashy swordsmanship isn't something one person can pull off on his own."
"Stand down, Sanemi!"
Gyōmei rose to his full height, beads clicking together, body like a living wall between Ubuyashiki and the brewing fight.
"This is the Lord's presence," he said. "Not a place for you to run wild."
Kagaya patted Gyōmei's arm.
"I don't believe Kyojūrō would harm me," he said softly.
He let go of Amane's support and slowly walked forward on his own power, body frail but will clear.
Standing before Rengoku, he smiled.
"Kyojūrō. I heard you once sought sword instruction from Roy," he said. "Is it him?"
"One servant cannot serve two masters. If it is Roy you've chosen, then… go with him," Ubuyashiki said gently.
"Lord!"
Sanemi had just risen when Rengoku suddenly dropped to his knees, his forehead pressing to the floor in a deep dogeza bow.
His voice rang out:
"As long as I live, I am, and will always be, a man of the Demon Slayer Corps.
"I will never betray you, Lord."
He lifted his head, eyes blazing.
"But… there is something more important I must do."
"And what would that be?" Gyōmei asked.
"What did Roy tell you that day beneath the wisteria?" he continued, fingers moving over his beads. "What can he offer you that we cannot? Enlighten us, please."
Kamado Roy.
His face and voice rose in everyone's minds.
Even Giyū, standing at the rear, could feel the attention shift his way.
Ubuyashiki did not interrupt this time—truthfully, he wanted to know as badly as anyone.
What had that boy said to Rengoku to make him change so much, so quickly?
Rengoku didn't answer with words.
He simply took a breath… and opened his chakra—
No, in this world's terms, his spiritual gates.
Waves of invisible pressure rolled out as he quietly began to breathe.