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

Shinobu Kocho wasted no time. Using the Kasugai crow, the Demon Slayer Corps' special communication bird, she relayed the intelligence straight back to Headquarters.

At the Demon Slayer Corps HQ, Kagaya Ubuyashiki—the clan head, his face ravaged with burn-like scars above the eyes—was caught slightly off guard when he received her report.

"A mysterious human… capable of controlling ice, with swordsmanship so precise he killed an enhanced demon in a single strike?"

As he quietly pondered the report, his wife, Amane Ubuyashiki, gently set a tray of food before him, her voice soft yet clear.

"That's quite the rare tale. I've never heard of anything like that."

Kagaya nodded slowly. "Indeed… It's certainly worth investigating."

What bothered him wasn't just the sheer power the man displayed. No—what truly piqued his interest was the question that followed.

Why would such a powerful individual be interested in someone like Tanjiro?

Had he discovered something…?

After all, that boy wasn't just any swordsman—he was a demon slayer traveling with a demon.

Not long after, a Kasugai crow arrived once again—this time bearing a direct order from Kagaya himself.

"Message from the Master! Message from the Master!" the crow cawed, fluttering in front of Shinobu. "The Insect Hashira, Shinobu Kocho, is hereby assigned to investigate the identity, origin, and objective of this mysterious individual!"

Then, after relaying the order, the crow continued with more news—an update on the current whereabouts of Demon Slayer Corps member, Kamado Tanjiro.

As soon as Shinobu received the information, she departed without delay.

---

Meanwhile…

Ron had been on the move all day, wandering from town to town, passing through one sleepy village after another. By now, he'd grown completely bored of the local dishes and weak liquor that every rural place seemed to offer.

Craving something fresh—something exciting—he found himself in the heart of Japans most dazzling city:

Tokyo Prefecture – Asakusa.

This place was unlike anywhere else he'd seen. Far more modern than any village or town he'd visited so far. People wore Western clothes, electric lights bathed the streets in brightness, railcars and steampowered autos chugged along the tracks—foreign novelties were everywhere.

Even at night, the city pulsed with energy—bright lights, endless traffic, and a constant stream of people weaving through the streets.

Compared to this, the rest of the country felt like it was stuck a hundred years in the past.

That evening, Ron stepped into a brightly-lit eatery. Inside, he ordered a bottle of shochu (a Japanese alcoholic beverage) and a sizzling hot plate of tonkatsu—freshly fried pork cutlet. As he ate, his face lit up with genuine delight.

"Ahh… Meat really is the best."

"Haha! You've got good taste, customer!"

The burly, cheerful shop owner chuckled as he placed a small plate of dark sauce in front of Ron.

"Try it with our house sauce. Brings the flavor to a whole new level."

Ron dipped a slice, took a bite—and his eyes immediately widened.

"Oh? You're right. That's really good."

The tonkatsu had a flavor distinct from the grilled meat he was used to in the world of pirates—it had a crispy crunch and a savory richness that was altogether unique.

Hearing the praise, the owner grinned from ear to ear.

"Right? I told ya!"

Ron finished off the entire plate in just a few more bites. Setting down his chopsticks, he glanced toward the counter.

"Hit me with another round."

"You got it!"

After leaving the restaurant, Ron stepped out into the cool night air, looking thoroughly satisfied.

"It's been a long time since I've had such a satisfying meal."

He glanced across the street, spotting a Western-style restaurant and a curry shop not far away.

With a smirk, he muttered, "Looks like I'll be sticking around for a few more days."

As he strolled through the bustling streets, a variety of local treats in hand, Ron casually wandered from stall to stall.

At the same time, he quietly expanded his immense Observation Haki—casting a wide net across the entire city.

"This place… really is crawling with demons."

His senses locked onto one powerful presence.

"That must be Kibutsuji Muzan…"

"The being that transcends all demons… a creature infinitely close to perfection, huh?"

He could understand why humans in this world saw him as a nightmare.

"But to me… he's nothing more than a one-swing problem."

With a faint smile, Ron continued observing.

Using his Observation Haki, he watched as Muzan, cloaked in the skin of a human male, lived his lie—a husband and father hiding in plain sight.

All the while, Muzan remained blissfully unaware…

That someone had already found him.

The difference in strength between the two sides was like the gap between worlds.

If Ron truly wanted to, he could've drawn his blade and ended it right here and now. Kibutsuji Muzan? Infinite cellular regeneration? Not a chance.

With the sheer might of Ron's current physique, even a single punch would be enough to obliterate Muzan—so completely that not even a speck of his cells would be left behind.

But honestly… where's the fun in that?

He had to stay in this world for at least thirty more days.

And this was only day six.

Already, boredom had begun to creep in.

If the plot of Demon Slayer hadn't even properly started yet, and he just sliced the final boss in half already… that would be beyond dull.

Being too powerful came with its own kind of problems.

Ron let out a long sigh in his mind.

"Gotta find something to keep myself entertained."

Finishing the last bite of a skewer, Ron turned and began walking in a new direction.

He was headed toward a certain hidden residence.

Tamayo's.

Before long, he left behind the dazzling lights and noise of the commercial district, stepping into a narrow, dimly lit alleyway.

The crowd thinned out quickly.

As he approached the concealed door tucked away at the end of the alley, a bald man—running a soba (Noodles) stall in the small clearing beside the street—looked up and saw him coming.

Business hadn't been good. His stall was nearly empty.

But when he saw Ron's towering figure, his eyes lit up.

"Customer! Would you like a bowl of soba? It's really good!" he called out, quickly hurrying over.

Ron glanced down at the man.

He was short—barely around 160 centimeters—and now found himself staring up at a young man who stood well over two meters tall with a naturally imposing air. The contrast was... overwhelming.

"W-Whoa! So tall!"

The bald stall owner instinctively took two steps back, gulping nervously as he tried to get a good look at Ron's face.

Ron recognized him.

Wasn't this the very same soba vendor who had that brief encounter with Tanjiro and Nezuko in the original story?

Ron walked over to a bench and sat down.

"In that case, I'll have a bowl of grated yam soba."

"O-Oh! Got it, right away!"

…

As Ron quietly enjoyed his soba, elsewhere in Asakusa—inside a grand Western-style mansion nestled deep within the city's opulent heart—Kibutsuji Muzan, masked in the form of a refined human man, flipped through a thick book in his study.

"The Blue Spider Lily… Where is it hiding?"

…

At that same moment, Tanjiro, who had just received his newest mission orders, was speeding toward Asakusa with Nezuko on his back.

Not far behind, Shinobu Kocho was on his trail, bringing her apprentice, Kanao Tsuyuri, along with her.

This city, dressed in glitter and glamor yet hiding so many man-eating demons beneath the surface…

Was about to face a gathering storm.

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