One Piece: With Sign-in System

After everyone had gathered at the Ubuyashiki estate, Ron led the group toward the mountains in the back.

Along the way—

Shinobu Kocho and the other Hashira began to explain the situation to the still-confused Tanjiro and his companions.

"This time, you've all been called here to join the special training."

"Special training?"

Tanjiro blinked in surprise.

Zenitsu clapped his fist into his palm as though a lightbulb had gone off. "Oh! I get it! The Hashira are gonna train us, right?!"

But Shinobu gently shook her head. "No. Just like you, we are the ones being trained."

Zenitsu froze for a second—and then his jaw dropped. "...Eh?! The Hashira are getting trained too?!"

Shinobu smiled and nodded. "Mr. Ron will be training us Hashira personally. It was also his idea to let you three join."

Zenitsu and Genya, who was standing not far behind, both looked ahead at Ron's figure with shocked expressions.

That man... is going to train the Hashira?

Tanjiro and Inosuke, who had already witnessed Ron's strength firsthand, didn't seem nearly as surprised.

In fact, Tanjiro was brimming with excitement.

Training under Mr. Ron… what would it be like?

It had to be something that would make him stronger.

If I could become even half as strong as him… then I'd be able to protect the people who need me. I might even be able to defeat that monster…

…

Eventually, they reached a clearing deep in the mountains.

Ron came to a stop.

"We're here."

The Hashira, along with Tanjiro and the others, also came to a halt.

Tanjiro looked around. It was nothing more than a vast, empty stretch of barren land.

With his booming voice, Kyojuro Rengoku called out, "Mr. Ron! What exactly will this training involve?"

Everyone else turned to look at him as well.

Ron cast a sideways glance at them. "No need to rush."

In the next instant, a flash of brilliant light passed through his deep blue eyes.

Hummm—

A powerful, invisible ripple of energy surged outward, instantly engulfing the entire hundred-meter clearing.

Before they could even process what had happened, Tanjiro, Zenitsu, and the rest suddenly felt an unbearable weight slam down on their shoulders—flattening them to the ground!

Even the Hashira themselves were bent under the pressure, their faces straining as they struggled to stay upright.

Further away, Gotou—who was luckily outside the affected area—stared at the scene with eyes wide in disbelief.

"Wh-what… what the hell is happening?!"

Pressed down by the overwhelming force, Tanjiro gasped. "This is… gravity?!"

Zenitsu's face turned pale as he trembled under the invisible weight. "It's so heavy! I can't even lift my arms!"

Inosuke and Genya gritted their teeth, trying to push themselves upright with trembling arms—but the effort was agonizing, and their faces were twisted in strain.

Of the younger group, Kanao held out the best. She managed to rise halfway, propping herself up with her Nichirin Blade as she knelt on one knee, visibly shaken but enduring.

As for the Hashira—

Only Tengen Uzui, Mitsuri Kanroji, and Obanai Iguro were still partially hunched over.

Rengoku, Muichiro Tokito, Genya, and Shinobu—though initially buckled by the sudden pressure—had quickly straightened their backs and now stood tall, their postures firm despite the crushing weight.

Genya cast a sidelong glance at Shinobu.

Wasn't her body supposed to be weaker than the others'? Since when had she become this strong? Was it because of her time spent beside that man?

"This gravity… really is something else. I'd say it's about seven to eight times stronger than usual."

Clad in his flame-patterned haori, Rengoku gripped his Nichirin Blade like a staff, eyes blazing with fighting spirit as he looked toward Ron. "To train under this kind of gravity… it'll definitely be twice as effective!"

"Correct," Ron replied calmly.

"Under this pressure, you'll spar and sharpen your swordsmanship. This is the training for the Hashira."

Ron stood smiling at them calmly.

"As for you five—Tanjiro and the others—your task for now is to get used to the gravity."

Tanjiro, still struggling to support himself under the invisible weight, responded with effort,

"Understood…!"

And so, under the oppressive weight of Ron's summoned gravity, the special training began.

Rengoku faced off against Sanemi Shinazugawa.

Shinobu Kocho took on Muichiro Tokito.

Tengen Uzui clashed swords with Obanai Iguro.

And as for Mitsuri Kanroji… she trained directly with Ron, who drew his sword to spar with her personally.

Under such immense gravity, even the Hashira—the finest swordsmen in the Demon Slayer Corps—found their hands trembling as they swung their blades.

Their movements were sluggish, their techniques dulled.

They had to fully activate their Breathing Techniques just to manage a single, complete form.

Sword styles that were once polished to perfection now faltered and broke down under pressure, filled with holes and hesitation.

To an outsider watching, the Hashira's swordplay might have seemed pathetic.

Sanemi gritted his teeth, both hands gripping the hilt of his blue Nichirin Blade, and roared as he slashed at Rengoku with Wind Breathing: Third Form – Clean Storm Wind Tree!

But before his strike could fully materialize, the arcs of wind energy collapsed into nothing.

"Damn it…!" Sanemi cursed, furious with his own body's limitations.

The other Hashira fared no better.

Meanwhile, Tanjiro and the rest had finally, after a great struggle, adjusted somewhat to the gravity.

No longer plastered flat against the ground, they had managed to lift their upper bodies and now knelt, propped up by their swords, gasping.

"Even in this condition… they can still move like that… They really are the Hashira," Zenitsu panted, his voice strained.

Tanjiro clenched his jaw, sweat pouring down his face as he gripped his sword, his eyes burning with resolve.

"We have to adapt… We must catch up…"

Inosuke was trembling violently, every muscle in his body twitching under the strain. Sweat poured off him like a waterfall.

Kanao and Genya were in similar states—utterly exhausted, but still holding on.

Ten minutes passed.

The Hashira were beginning to show signs of fatigue, their brows furrowed, faces tight with strain.

The five junior Demon Slayers gritted their teeth and continued to push through.

Thirty minutes in, the Hashira were panting heavily, sweat soaking their clothes.

Tanjiro's group was drenched and shaking, barely managing to keep upright.

One full hour later…

"That's enough. We'll stop here for now."

Ron dispelled the gravity field with a flick of his will.

The pressure vanished instantly.

The Hashira, too drained to even raise their swords again, slumped to the ground, breathing hard, their bodies soaked in sweat.

Tanjiro and the others, who had just begun to get their footing, collapsed completely.

"I'm done for… I can't even lift a finger…"

Zenitsu lay sprawled on the ground, tongue hanging out like a lifeless dog.

Tanjiro was equally wiped out.

"My Breathing Technique went into overdrive… It feels like my lungs are on fire…"

"Ughhh…"

Inosuke lay flat on his back, arms and legs splayed out, chest rising and falling like he'd just run a hundred miles.

Kanao and Genya weren't in much better shape. They, too, lay breathless and beaten.

From the edge of the field, Gotou—who had come to deliver food and water—stared at them in horror.

"This… this is what their special training is like? That's terrifying…"

…

After a period of rest, food, and rehydration, everyone slowly recovered their strength.

Then Ron raised his hand and, before their stunned eyes, a life-sized combat doll—the Yoriichi Type Zero borrowed from the Swordsmith Village—appeared out of thin air in the center of the clearing.

"Tanjiro, you five will take turns training with this."

After teaching them how to use it, the five juniors eagerly gathered around, full of curiosity and anticipation.

Then, turning his gaze to the Hashira, Ron placed his hand on the hilt of the ancient sword at his waist.

With a smile, he said,

"You've all recovered by now, haven't you?"

"Good. Then it's time for the next phase…"

"All of you—come at me, together."