"Hm?"
Tengen nodded through the first half of Chika's plan, but the moment she mentioned bringing her "little brothers," he blinked in surprise. Then again, after a moment of thought, he realized it was completely in character.
"Chika… has anyone ever told you you're a brother complex?"
"Nope. You're the first."
She didn't even blink at the jab—which, to her, meant he'd agreed.
===
Yoshiwara—the Entertainment District.
The government called it "legal," the world called it "sinful," and those who'd seen its night-lit streets called it beautiful. A city that reversed day and night, dressed in glitter and illusion.
And that was where they were heading next.
After saying her goodbyes to Tengen, Chika returned to her quarters at Corps Headquarters. The clang of training swords echoed through the yard—Tanjiro and the others were in the middle of their drills.
Tanjiro, especially, burned with focus.
He had inherited the strongest of all Breathing Styles—the Dance of the Fire God—and refused to tarnish its name.
As he moved through the forms, his mind replayed Akaza's battle like a living memory. Even though he hadn't joined the fight, every swing and step had seared itself into his heart.
He imagined facing that overwhelming strength himself—Akaza's fists like thunder, the pressure enough to choke him.
Even in a dream, he couldn't last more than a few exchanges. If Akaza ever used the techniques he had unleashed on his sister—Destructive Death: Annihilation Type and Final Form—Tanjiro knew instinctively he'd die instantly.
But there was something else he couldn't stop thinking about—Akaza's words to Rengoku.
"You're nearing the Supreme Domain."
That phrase wouldn't leave his mind.
His father had once spoken to him about something called a "domain," too… though that had been long ago. His memory of it was hazy now.
"I wonder if Sis ever heard Father mention it…" Tanjiro murmured, unaware that Chika was silently walking up behind him.
"Yo~ what's got you frowning so hard?"
Her sudden voice nearly sent Tanjiro face-first into the dirt. The poor boy, still drained from training, barely caught himself before he fell. The sight startled Chika in turn.
Scaring him was one thing—watching him eat dirt was another.
She quickly caught his arm. "You good? You look exhausted—you didn't even notice me coming up."
"It's because you hide your presence too well, Sis."
He took her hand and stood up, smiling awkwardly.
Chika tilted her head. Hide my presence? I wasn't even trying to.
They both shrugged it off.
Then Tanjiro suddenly remembered what he'd been pondering and looked up. "Right! Sis, have you ever heard Father talk about something called a 'Domain' before?"
"Domain?"
Chika blinked. The original owner of this body had no such memory—but she immediately guessed what he meant.
The Transparent World.
Tanjiro and Chika's father, Kamado Tanjūrō—frail, sickly, coughing blood more often than not. Yet despite that, he could dance the Fire God's Kagura beneath falling snow for an entire day and night without tiring.
He'd never joined the Demon Slayer Corps, never studied swordsmanship, never even seen a demon.
And yet—his state of being had surpassed what even the Hashira called attainable.
The name of that realm was The Transparent World.
Ten days before his death, a massive bear had appeared near their mountain home. Fearing it might attack his family, Tanjūrō took up a single axe and stepped outside.
Tanjiro, watching from afar, had trembled at the sheer size difference—the beast's claws could have torn a man in half. But his father… his father had simply moved.
With one quiet breath, he leapt higher than the bear's head—
—and the next instant, the beast's skull split clean in two.
That image had burned itself into Tanjiro's memory forever.
At the time, he hadn't understood what he'd seen. But later, when he heard Akaza speak of "The Supreme Domain," he couldn't help but recall it.
Chika, meanwhile, smiled faintly.
She didn't really remember Tanjūrō saying any of this, but she wasn't about to admit that.
"Oh, that. Yeah, I've heard of it—it's called the 'Transparent World,' right? Now that you mention it, Father's explanation was actually kind of interesting…"
Feigning realization, she paraphrased the old man's words as best she could, piecing together what Tanjiro had once been told.
And as she spoke, Tanjiro's eyes lit up.
"Sis! Akaza said Rengoku was approaching the Supreme Domain—do you think that's related to the Transparent World Father mentioned?"
"Maybe…?"
Her tone was deliberately vague—not because she wanted to act mysterious, but because she genuinely wasn't sure.
Akaza's "Supreme Domain" came from observing Rengoku's burning aura, while the Transparent World was about emptying oneself, erasing breath and self-awareness entirely. One burned like the sun; the other flowed like still water.
But if the path of martial perfection truly led to returning to the origin—to absolute clarity—then yes, perhaps they were connected.
Either way, the Transparent World was worth mastering.
And if Tanjiro could rediscover it, that would save her the trouble of introducing it later to the rest of the Hashira like she'd done with the Crimson Blades.
First the Hono no Kagura, then the marks… now the Domain. Catch 'em all like Pokémon, she thought wryly.
Still, there was work to do.
She cleared her throat. "Anyway, go round up the others. We've got a new mission."
"Mission? Got it!"
Tanjiro nodded eagerly and dashed toward the mansion. Since the Mugen Train incident, nearly two months had passed—months of nonstop training. He was itching to see how far he'd come.
Watching him disappear into the distance, Chika couldn't help but smirk.
Of course she knew what was going through his head.
And somewhere, far away in Yoshiwara, a courtesan named Daki suddenly shivered—an icy chill running down her spine, as if the world itself had just turned its eyes upon her.