One Piece: With Sign-in System

Over on Tanjiro's side—

Even though he could now see the arrows, his movements and speed still couldn't keep up with the bizarre trajectories they followed. A single misstep, and the arrows would latch onto him, sending him hurtling in all directions. Tanjiro could only rely on his Water Breathing derivative techniques to counteract the force and soften the impact.

Butterfly Shinobu withdrew her gaze from the chaotic battlefield, tilting her head toward Ron and asking, "Earlier, you said you could help me grow strong enough to kill that man… How exactly do you plan to do that?"

Ron smiled at her and said, "Before I answer, you need to understand two things first."

"What things?" she asked, frowning slightly.

"First question," Ron said, his tone casual but sure. "For a swordsman, what determines their strength?"

"Probably… talent and hard work?" Shinobu answered after a moment's thought.

Ron gave a slight nod, neither agreeing nor denying it. "Second question: as a swordsman, how does one truly become stronger?"

"By relentlessly honing their swordsmanship day and night, and gaining experience through battles," she replied without hesitation.

"Not bad," Ron said, smiling wider, "but you're still missing something."

Shinobu tilted her head up, studying the side of his face with a furrowed brow. Tamayo and Yushiro also turned their attention to Ron, curiosity flickering in their eyes.

Ron, still gazing toward the battlefield, spoke calmly, "In my view, for a swordsman to grow stronger, they must develop in four areas."

"Body, Technique, Skill, and Will."

"Body refers to physique. For a swordsman, a powerful body is vital. And breathing techniques, which enhance the body, are incredibly important. Each person's physique suits different forms of Breathing."

"Technique refers to swordsmanship — your mastery over your Breathing Style and its derivative forms. Whether you can flow smoothly between techniques, whether you can adapt your moves in response to the situation… just like what Tanjiro is doing right now. He's weaving through different techniques during the fight, deepening his understanding with each clash."

At this, Yushiro glanced toward Tanjiro. From the start of the battle till now, Tanjiro had already cycled through dozens of sword techniques, and two of them even showed signs of merging together — an impressive feat.

"Skill," Ron continued, "refers to tactics and experience. For example, Shinobu, the poison laced into your sword and the lightness of your footwork — these are all part of Skill."

"And Will... Will encompasses battle spirit, killing intent, resolve, even the acceptance of death. It's the strength drawn from the heart. When the heart is unbreakable as iron, and one strikes with unwavering determination, it can unleash strength far beyond one's limits."

As he spoke, Ron glanced sideways at Shinobu.

"The man who created the original Breathing Techniques and established the entire system — Yoriichi Tsugikuni — was a swordsman who reached the absolute pinnacle in Body, Technique, Skill, and Will."

"Four hundred years ago, while still human, he single-handedly defeated Muzan Kibutsuji… and came within a hair's breadth of completely destroying him."

At these words, Shinobu's eyes widened in shock, her heart shaken to its core.

Tamayo stood silently, lost in memory, recalling the figure of a man wielding a crimson blade and wearing a pair of hanafuda earrings. That single encounter had given her — trapped in despair — a glimpse of hope that Muzan could one day be defeated.

If only… if only he had finished it back then…

Ron's gaze remained fixed on the battlefield, where Kanao struck down the Temari demon with a clean slash to the neck, while Tanjiro managed to sever the Arrow demon's head — though he was still being hurled uncontrollably in the aftermath by the demon's final, desperate attack.

"Shinobu," Ron said suddenly, his tone drawing her back, "if a swordsman pushes their mastery of Breathing Techniques to the limit, burning through their very blood and life force for strength… do you know what happens then?"

Shinobu shook her head, lips pressed into a thin line.

Ron turned to her, smiling softly. "Then the swordsman will manifest a Mark — a pattern upon their body. But it comes at a price. Those who awaken the Mark are, in essence, sacrificing their lifespan for power. Most don't live past the age of twenty-five."

Butterfly Shinobu stared blankly at Ron. It was the first time she had ever heard of such a thing.

"A swordsman who reaches the peak of clarity in battle," Ron continued, "will also step into an entirely new realm…"

Under Shinobu's dazed gaze—

Ron calmly uttered two words.

"Transparent World."

"When your mind becomes as clear as glass, you will be able to see the Transparent World," he said.

"If you can reach that realm, it means you'll be able to perceive everything inside a demon—their organs, the flow of their blood, the movement of their muscles—every minute detail crystal clear before your eyes. Time itself will seem to slow down, and every action of your opponent will be completely within your grasp. If you achieve this state, even a frail, dying human could take down a raging bear with ease."

Ron turned slightly and gave Shinobu a soft smile.

"Butterfly Miss, if you can reach that realm... you might just be able to kill Doma."

"Transparent… World."

Shinobu whispered it silently in her heart, a faint gleam lighting up her violet eyes.

"But," Ron said, "it's not something easily attained. Only those with the right talent, who have pushed themselves to their very limits and tasted the bitterness of countless failures, have the chance to set foot into that domain."

Yushiro couldn't help but blurt out, "Then... have you reached it?"

Ron's demeanor was as light as the wind, and he answered as if it were the most natural thing in the world:

"Of course."

Yushiro froze, his mind blank.

Tamayo and Shinobu both looked at Ron with undisguised shock in their eyes.

But Ron ignored their reactions, his voice calm and steady as he continued,

"When your intent—your will—reaches a certain level, a phenomenon will occur. That phenomenon will manifest on your blade."

"On the blade?"

The three of them looked confused.

Ron smiled slightly and reached his hand toward Shinobu.

"Lend me your sword for a moment."

Shinobu hesitated, but after a brief moment, she handed over her Nichirin Blade.

At that moment, both Kanao and Tanjiro returned, carrying the blood samples of the Temari Demon and Arrow Demon.

One of them looked perfectly fine, while the other had to crawl back, looking extremely battered.

"I've brought the blood back—huh? What are you all doing...?"

Before Tanjiro could even finish his sentence—

His gaze locked onto Ron, who was gripping Shinobu's thin Nichirin Blade, and he watched in astonishment as the blade began to change color.

In just a few breaths, the originally violet blade turned a brilliant crimson red, radiating a fierce, burning heat!

"!?"

Everyone present gasped at once.

"The blade... turned red?!"

Tanjiro's jaw dropped in disbelief.

Even Kanao's usually calm expression shifted in surprise.

Tamayo's eyes widened, and she stared at the crimson blade in Ron's hand as if she had seen a ghost.

"This color… like it's burning with real flames… even the smell of it, like scorched metal... It's unmistakable! It's exactly the same as that man's sword from long ago!"

Yushiro gulped hard. As a demon himself, he could feel a terrifying sense of danger emanating from the sword in Ron's grasp.

"W-what... what is this?!"

Shinobu finally couldn't hold back and asked aloud.

Under everyone's stunned gaze—

Ron smiled, gripping the Crimson blade firmly.

"This is called the Crimson Blade—the Scarlet Nichirin Blade. Against demons, it carries devastating power. Even Muzan himself would be wounded by it, and the injuries it causes are extremely hard to heal."

He casually sheathed the burning Crimson blade back into its scabbard and handed it back to Shinobu.

"However," he added lightly, "turning your Nichirin Blade into a Crimson Blade isn't something that happens easily. There are two critical conditions."

Tanjiro, unable to contain his curiosity, asked eagerly,

"And what are the two conditions?"

Ron turned to him with a smile, his voice low and steady:

"Incredible arm strength... and a strong, unwavering heart."

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