Sign-In System: One Piece, Demon Slayer & Beyond

One day later—

In a bustling town that still held some degree of prosperity,

The streets were bustling with people dressed in traditional kimonos and wooden geta sandals, reflecting the fashion typical of Taishō-era.

A few individuals wore Western-style clothing, but they were a rare sight.

Inside a lively tavern doing brisk business,

A handful of locals sat around with drinks, chatting in hushed but tense tones about a recent string of deaths.

"Hey, did you hear? Another kid went missing last night."

"Yeah, yeah, I heard. It was that house near the northern foot of the mountain, right?"

"That's the one. Both their kids vanished overnight."

"That makes four cases this month already, right? And they still haven't caught the culprit? What the hell are those lazy cops even doing?"

A burly man slammed back the last of his sake, slurring as he ranted with drunken annoyance.

Across from him, his companion looked around nervously. "Shhh! Don't go spouting stuff like that out loud…"

"It's fine, it's fine. Not like they can hear us," the drunk chuckled, giving his thigh a hearty slap before leaning in closer, his face full of mystery.

"But you know what? I heard a rumor about those disappearances…"

"What kind of rumor?"

Lowering his voice and glancing around, the drunk whispered conspiratorially,

"People are saying… it's the work of a demon that eats children."

"A demon? Ha! Come on, don't give me that. There's no such thing as monsters or demons in the real world. Can't believe you'd fall for that nonsense."

"I don't believe it either," the man admitted. "Just repeating what I heard."

…

By the window,

Ron sipped some Wine, quietly watching the flow of people outside while listening to the ongoing conversations.

And just from those snippets,

He already had a pretty solid idea of where he was.

"So this is… the Demon Slayer world."

"To think I'd actually end up in the world where the Sun Breathing technique originated… This must be fate."

A faint, intrigued smile curled at the edge of Ron's lips as he lifted his cup.

"How interesting."

After finishing his drink,

Ron placed a few coins on the table and walked out of the tavern.

"Take care now!"

The young waitress watched his back with a curious gleam in her eyes.

"That young man… He doesn't look like he's from around here. Could he be from overseas?"

…

"So, this is the world of Demon Slayer… The power levels here are relatively low."

With the Endless Flask still fastened to his belt, Ron strolled casually down the street, mentally reviewing what he remembered about the world's structure.

The Taisho Era—

A time when Japan was slowly being westernized, but still clung to its traditional roots.

In this world, humans and demons coexisted in shadows.

Though tales of demons—man-eating creatures that stalked the night—circulated in old legends and elders' whispers,

Their existence remained unknown to the general public.

At the top of the demonic food chain stood Muzan Kibutsuji, the progenitor of all demons,

Who created more of his kind by injecting his blood into humans.

Demons fed on human flesh, and when starved, would lose their minds and go berserk. Their strength was tied directly to how much of Muzan's blood they had received—And how many humans they had consumed.

The stronger ones awakened strange supernatural abilities known as Blood Demon Arts. They had inhuman regenerative powers, were immune to most damage, and could even survive decapitation—But exposure to sunlight would instantly reduce them to ash.

The most powerful of these demons served under Muzan, a group of twelve known as the Twelve Kizuki, split into Upper and Lower Ranks.

Opposing them was a secret, centuries-old organization dedicated to eradicating demons: the Demon Slayer Corps.

Its combatants were known as Demon Slayers,

Divided into fighters who took down demons and support units known as the Kakushi who handled cleanup.

Beneath the leader of the corps were the nine strongest swordsmen—the Hashira, or Pillars.

They honed their bodies through rigorous training, mastering specialized breathing techniques and sword styles.

Using Nichirin Blades, forged with ore that had absorbed the essence of the sun, they could kill demons that even the sun itself feared.

As Ron recalled these details,

He glanced at the traditional architecture around him and mused to himself—

"Yeah… this definitely isn't the era of Yoriichi Tsugikuni."

"So what time period is this? Has the main Demon Slayer story already begun? Or is it still in the calm before the storm?"

A thoughtful look crossed Ron's face.

"Guess I'll need to investigate and find out."

Suddenly—

He seemed to sense something. His eyes shifted sharply toward the north side of town.

"That presence…"

By unleashing Observation Haki, extending its reach across several kilometers—

Ron "saw" a distant scene play out in his mind.

And with a faint, knowing smirk on his face, he murmured—

"So… the Demon Slayer Corps has shown up."

In the northern part of the city, inside a modest residential home...

Several members of the Demon Slayer Corps, all clad in the organization's signature uniform, were carefully inspecting the premises.

"There's definitely a demonic presence here."

"No mistake about it—it's that same demon we've been tracking."

"You sure we shouldn't alert the higher-ups about this?" a female member asked with a worried expression.

"We'll be fine," replied a short-haired male slayer with supreme confidence. "We've already fought it once before. It didn't stand a chance against us."

"Even so..." she mumbled, still looking uneasy.

An older, taller, and leaner male slayer standing beside her gently patted her on the shoulder.

"Yukita, I get where you're coming from. That demon has devoured quite a few people lately—its strength has definitely grown. This mission is dangerous. But as members of the Demon Slayer Corps, we've got to learn to face that danger. We can't always rely on the big shots. If we don't push ourselves, how are we supposed to grow stronger?"

"And besides," he added, "Lady Shinobu is currently scouting just over that mountain nearby. If anything does go south, she can rush over in no time. We've got her backup."

Hearing that, a flicker of determination lit up in Yukita's eyes.

"Alright. Then let's do this. Let's finish that demon off once and for all."

"Yeah." The tall slayer nodded approvingly with a small smile.

"Speaking of which..." The short-haired slayer crossed his arms and gazed out the window. "What did happen up there in those mountains anyway? Something big enough that one of the Nine Hashira—Lady Shinobu herself—had to step in?"

"Don't tell me..." Yukita's voice dropped slightly. "Could it be one of the Twelve Kizuki?"

The older slayer shook his head. "If one of the Twelve appeared, it wouldn't be this quiet. Whatever's happening on that mountain... it's something else. And honestly, it's not our concern. Let's focus on the demon right in front of us."

"Understood!"

…

Meanwhile, in a remote, snow-covered mountain forest...

Amid the quiet stillness stood a woman with long black hair tinged with purple at the ends, her violet eyes sharp and discerning. Her hair gently brushed her collarbones. She wore the standard uniform of the Demon Slayer Corps, over which she draped her iconic butterfly-patterned haori. In her hand rested a delicate, needle-thin Nichirin Blade.

Butterfly Hashira—Shinobu Kocho.

She stood at the edge of a massive rift in the earth—nearly a hundred meters long and over ten meters deep. Her usual gentle and serene expression had vanished, replaced by a heavy, furrowed look.

"What in the world... caused this?"

Could this be the work of some Blood Demon Art?

The thought flashed through her mind, but even she found it hard to believe.

No...

How could there be a Blood Demon Art capable of producing destruction on such a massive scale?!

She narrowed her eyes, the icy wind lifting her haori as she stared into the yawning abyss in front of her.

Something was very, very wrong.