Deep within the mountain canyon training camp, the oppressive atmosphere that had lingered for days seemed ready to ignite the air itself.
Clang! Clang! Clang!
The deafening sound of blades colliding rang across the rocky clearing, sparks scattering in all directions.
The Wind Hashira, Sanemi, stared wide-eyed, gripping his Nichirin Blade tightly as violent cyan currents of wind swirled along its edge.
The windmill-shaped Demon Slayer Mark on his right cheek had fully manifested. With every breath, its color deepened, feeding him a constant surge of explosive power.
"Wind Breathing, Eighth Form: Primary Gale Slash!"
Sanemi's figure turned into a raging whirlwind, sweeping across the ground at a speed barely visible to the naked eye, his blade aimed straight for his opponent's throat.
Facing this attack, powerful enough to tear through stone, the Water Hashira, Giyu, showed no intention of retreating.
On his usually expressionless face, a deep blue, wave-like Demon Slayer Mark had appeared on his left cheek. His gaze was calm as still water, his breathing steady and controlled, as he swung his deep blue Nichirin Blade upward.
"Water Breathing, Tenth Form: Constant Flux!"
A massive water dragon surged forth with his strike, spiraling outward as it collided head-on with the cyan wind blades.
Boom!
The shockwave burst outward, sending gravel flying in all directions. The Demon Slayer Corps members watching from the sidelines were forced to retreat again and again under the residual force, unable even to open their eyes.
The two fighters separated upon impact, sliding back several meters. After regaining their footing, they once again pointed their blades at each other, breathing heavily. Yet the Demon Slayer Marks on their faces remained stable, showing no signs of fading despite the intense exertion.
"And.. Stop."
A calm voice cut through the roaring wind and dissipating mist, reaching everyone present.
Rin sat atop a large fallen tree, idly tossing a small pebble in his hand.
At his command, Sanemi and Giyu immediately sheathed their Nichirin Blades.
The Demon Slayer Marks on their faces gradually faded as their breathing slowed, retreating beneath the skin.
"Not bad. You can now activate and deactivate them at will without losing control."
Rin flicked the pebble away, jumped down from the tree, and swept his gaze across the training ground.
The hellish training of the past month had produced remarkable results.
Not far away, the Stone Hashira, Gyomei, sat cross-legged beneath the pounding waterfall, the stone-like Demon Slayer Mark on his arms flickering in and out of view.
The Flame Hashira, Kyojuro, and the Sound Hashira, Tengen, were sparring, flame and sound-patterned marks appearing on their foreheads and around their eyes.
The Serpent Hashira, Obanai, and the Mist Hashira, Muichiro, trained on plum blossom stakes, their snake and mist-like marks reflecting off one another as they moved.
Even the Love Hashira, Mitsuri, whose physique was uniquely flexible, could now activate the pink, heart-shaped Demon Slayer Mark near her collarbone while wielding her flexible blade.
What surprised Rin slightly was Shinobu, standing by the corridor with a basin of water in hand.
Under the repeated refinement of Yang Release chakra, the muscle fibers that had once limited her due to her petite frame had been fundamentally reshaped.
While her raw strength still could not match that of the Flame or Wind Hashira, her speed had reached a frightening level.
Just yesterday, while attempting to pierce a specially forged steel plate, she had successfully manifested a purple butterfly-shaped Demon Slayer Mark along the side of her neck.
Every single one of them had awakened their mark.
Without a doubt, this was the most elite demon-slaying force in the thousand-year history of the Demon Slayer Corps.
"After a month of reinforcement with Yang Release, your bodies have fully adapted to the burden of the Demon Slayer Mark. Even if you fight continuously for three days and nights with the mark active, as long as your head remains attached, you won't die."
Rin stepped into the center of the training ground, gathering all the Hashira before him.
Everyone quickly gathered, with the three rising talents—Kamado Tanjiro, Agatsuma Zenitsu, and Hashibira Inosuke—also squeezing into the outer circle.
The three of them had awakened their Demon Slayer Marks a few days earlier and were currently in peak condition.
"Rin-dono, do we now have the strength to kill Kibutsuji Muzan?"
Rengoku Kyojuro stepped forward, his voice loud and resolute.
"Kill Kibutsuji Muzan?"
Rin glanced at him and poured cold water on his enthusiasm without hesitation.
"At your current level, if you encounter one of the top three Upper Ranks, you might be able to ensure your survival, or even win through numbers. But if you face Kibutsuji Muzan directly, the blades in your hands are no different from fire pokers."
Everyone's expressions shifted.
"Why?" Sanemi frowned. "With the Demon Slayer Mark, our speed and strength have increased several times over. No matter how strong Kibutsuji Muzan is, are you saying we can't even cut his neck?"
"You can cut it," Rin replied bluntly.
"But cutting it is meaningless."
Rin turned to Tomioka Giyu.
"Lend me your sword."
Giyu did not hesitate. He immediately drew his Nichirin Blade and handed it over with both hands.
Rin gripped the hilt, his fingers brushing across the cold steel.
"The top three Upper Ranks, including Kibutsuji Muzan, have already surpassed the limits of ordinary demons. Decapitation with a standard Nichirin Blade is no longer fatal to them. The moment your blade passes through his neck, Kibutsuji Muzan can regenerate instantly. Killing him through decapitation alone is impossible."
"Then what are we supposed to do?!" Uzui Tengen's expression grew serious. If even decapitation was ineffective, then the accumulated experience of demon slayers over the past thousand years would mean nothing.
"If you want to suppress their rapid regeneration, you need to change something about your blades."
Rin tightened his grip on the hilt.
In the next instant, the muscles in his arm tensed. A terrifying grip strength—purely physical, without any chakra—clamped down like a press.
An astonishing scene unfolded.
Before their eyes, the originally deep blue Nichirin Blade began to glow with a scorching crimson heat, spreading outward from the hilt.
The intense heat distorted the surrounding air. Even from several steps away, everyone could feel the scorching temperature radiating from the blade—enough to completely incinerate demon cells.
"This… the sword turned red?!" Tanjiro's eyes widened.
"This is a Bright Red Nichirin Blade."
Rin released his grip, and the crimson glow quickly faded, the blade cooling back to its original deep blue. He casually tossed the sword back to Giyu.
"A Nichirin Blade is forged from tamahagane that has absorbed sunlight. If your grip strength is sufficient, extreme pressure can generate intense heat, transforming the blade into a Bright Red Nichirin Blade. Any demon struck by it will have their wounds burned as if by real sunlight, completely losing their ability to regenerate."
"But… that kind of grip strength…"
Giyu stared at the blade in his hand. The force Rin had just displayed was beyond human limits. Even with the Demon Slayer Mark activated, he couldn't imagine exerting enough pressure to make steel glow red.
"If one person's strength isn't enough, then use a method."
Rin pointed at Sanemi and Giyu.
"You two—activate your Demon Slayer Marks. Use all your strength and clash your blades."
Sanemi and Giyu exchanged a glance, immediately understanding. If individual grip strength wasn't enough, then they would rely on the immense pressure and friction created by two blades colliding.
Both of them let out low shouts as their Demon Slayer Marks surfaced. Gripping their swords with both hands, they swung at each other with full force.
Clang!
A deafening metallic crash rang out.
Under the overwhelming pressure, a burst of brilliant sparks erupted at the point of impact. In the next instant, a scorching crimson glow spread rapidly from the collision point, engulfing both blades from end to end.
"It worked!"
Kanroji Mitsuri covered her mouth, her eyes filled with excitement.
Sanemi stared at the Bright Red Nichirin Blade in his hand, the intense heat radiating from it reflected in his eyes as a trace of exhilaration appeared. With this, Kibutsuji Muzan's rapid regeneration would no longer be an insurmountable obstacle.
"The Demon Slayer Mark. The Bright Red Nichirin Blade."
Rin stood with his hands in his pockets, watching the group of swordsmen who had finally stepped into the realm of top-tier combat power.
"There's one last thing. Sukitooru Sekai. (The See-Through World or Transparent World)."
"Let go of unnecessary killing intent. Focus your awareness to the extreme, and sense your opponent's muscle movements and blood flow. Only when you can close your eyes and perceive their internal structure as clearly as if it were laid bare before you will you be qualified to stand against Kibutsuji Muzan."
After explaining the final key, Rin turned and walked toward Kochou Shinobu, who was waiting by the corridor.
Kochou Shinobu handed him a clean towel.
"Have you taught them everything?" she asked softly, passing him a cup of warm water.
"I've taught them everything I can."
Rin wiped his hands, took a sip of water, and looked up at the sky above the canyon, broken into fragments by the canopy of trees.
"Now, it's only a matter of when that coward Kibutsuji Muzan decides to drag us into the game."
At that moment, a Kasugai Crow flapped its wings as it rushed in from outside the canyon, landing directly on a wooden frame at the edge of the training ground.
"Caw! Urgent report! Urgent report!"
The crow's hoarse, anxious cry echoed across the suddenly silent training ground.
"Message from the Master! Multiple hidden strongholds across the country have simultaneously discovered large numbers of mysterious eyeballs conducting surveillance! These eyes all bear the character 'Four'! The Kakushi attempted to eliminate them, but there are too many—it's impossible to destroy them all! Caw!"
Hearing this, every Hashira instinctively tightened their grip on their Nichirin Blades, their gazes turning toward Rin in unison.
Kibutsuji Muzan's surveillance had finally spread.
"A little slower than I expected."
Rin tossed the towel aside, a cold smile forming at the corner of his lips.
He knew this was the final signal.
Once Kibutsuji Muzan confirmed the exact location of the Demon Slayer Corps headquarters, he would undoubtedly activate his Infinity Castle and drag them all inside for a decisive battle.
"Everyone."
Rin turned, his black hair stirring in the mountain wind. Deep within his dark pupils, a scarlet six-pointed pattern faintly rotated.
"The special training ends here."
"Go back, prepare your weapons, and write your wills. Eat well."
He stepped forward, walking toward the exit of the canyon.
"Prepare yourselves."
"We're going to hell to kill demons."
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