In the early morning, dust rose across the training grounds behind the Butterfly Mansion.
Thud!
A heavy impact shattered the quiet of the morning.
Inosuke Hashibira, still wearing his wild boar mask, was sent flying like a ragged sack. His body traced a perfect arc through the air before crashing hard into the sand near the fence, kicking up a cloud of dust.
"That's the fifteenth time."
Rin stood at the center of the field, holding a dry branch he had casually snapped from a tree. His gaze swept over the other two boys standing opposite him, both gasping for breath.
Kamado Tanjiro gripped his wooden sword with both hands. Sweat streamed from his forehead down his cheeks, evaporating almost instantly when it touched the dry soil.
Beside him, Zenitsu Agatsuma's legs trembled even more violently. Even the way he held his sword had become crooked, and he looked as though he might burst into tears at any moment.
"Too slow. Too stiff," Rin said, pointing out their flaws without mercy. "Tanjiro, your Hinokami Kagura is indeed extremely powerful, but before every strike, your shoulder muscles tense up half a second too early. To a true master, that kind of wind-up is basically announcing exactly where you're going to attack."
"And you, blondie. Thunder Breathing is all about the explosive power of a single decisive strike. Yet you keep charging up and striking poses in place. If you faced a demon with a long-range Blood Demon Art, you would've been turned into a pincushion long ago. Blend the explosive force of thunder into your natural movement. Don't just stand there like a wooden post."
The two who had been called out looked miserable, yet neither of them even had the strength to argue.
Three days had already passed since the Mugen Train incident.
During these three days, Rin had officially taken over the combat training of the main trio.
"Again!"
Inosuke, who had been lying in the sand, flipped over and scrambled to his feet, two trails of white steam snorting from his nostrils.
Although he had been thrown around until he was dizzy, his naturally combative nature had been completely stirred up.
He crouched low, crossing his dual blades in front of him, then charged forward like a frenzied wild boar.
"Beast Breathing, Boar Rush—!"
Tanjiro also took a deep breath, forcing his aching lungs to push Total Concentration: Constant to its limit as he flanked from the side.
Although Zenitsu resisted with all his heart, he could only grit his teeth and turn into a yellow flash of lightning, attempting a surprise attack from Rin's blind spot.
Facing the three-pronged assault, Rin's eyes remained calm.
Relying purely on combat instinct, at the moment the three attacks were about to connect, his body tilted slightly at an angle that seemed to defy the laws of physics.
Inosuke's charge brushed past the edge of his clothes. Rin used the withered branch to lightly tap the back of Inosuke's knee. Inosuke instantly lost his balance and plunged headfirst into the dirt.
At the same time, Rin flicked his hand backward, catching the withered branch against the guard of Tanjiro's wooden sword. With a twist of his wrist, a precise surge of force numbed Tanjiro's hand and sent the wooden sword flying out of his grasp.
Finally, Rin glanced sideways at Zenitsu, who was rushing toward him like a bolt of lightning. He raised his left leg, stopping it less than a centimeter from Zenitsu's face.
The sharp wind from the kick stung Zenitsu's cheek, frightening him so badly that he collapsed onto his backside and let out a miserable scream.
"Combat over. Total wipeout."
Rin casually tossed the withered branch aside and turned toward the corridor.
"Hmm.. Your foundations are still too weak. That's it for this morning's sparring. Go run one hundred laps around the Butterfly Mansion. If you don't finish, no lunch."
Watching the three teenagers grumble while obediently getting up to run, Shinobu Kocho, who had been observing from the corridor, handed over a clean towel.
"Rin san~ Aren't you being a little too harsh on them?" Shinobu watched Rin wipe the sweat from his face, her tone teasing. "It's only been three days, and they already have so many bruises that even the Butterfly Mansion's special ointment can barely keep up. This doesn't really seem like your usual 'too much trouble' style."
"Glass must be forged in the fire before it can be polished into a gem."
Rin draped the towel around his neck and casually picked up a cup of cold tea from the table, draining it in one gulp.
"I don't know when the bait I cast will attract a big fish. Although that coward Muzan was fooled by me, the next ones he sends will definitely be the core fighters among the Twelve Kizuki. If these three kids can't even last three minutes against me, they won't even have the chance to draw their swords when they face a real Upper Rank."
At the mention of "Upper Rank," Shinobu's eyes narrowed slightly. She knew Rin was telling the truth.
The Demon Slayer Corps' current peace was only temporary. The calm before the storm often meant an even more brutal slaughter was coming.
"Don't worry."
Noticing the concern in her eyes, Rin reached out and lightly pinched her fair cheek. It felt soft and warm.
Before Shinobu could get angry and swat his hand away, he had already withdrawn it as if nothing had happened.
"If the sky falls, I'll hold it up. You just focus on making your medicine."
After saying that, Rin waved his hand and walked back toward his guest room.
Shinobu stood there, watching his tall, straight back as he walked away. The scolding she had prepared got stuck in her throat. She bit her lower lip, her cheeks slightly flushed, and murmured to herself, "That guy… always so self-centered."
…
Night fell.
Inside his room at the Butterfly Mansion, Rin sat cross-legged on the tatami with his eyes tightly shut.
The doors and windows were locked. No one was around to disturb him.
"System, open the panel," he thought silently.
A deep blue virtual screen instantly appeared before him. The bottom row clearly displayed his current assets.
[Dimension Points: 51,990]
Since transmigrating into this world, by altering the Hand Demon incident, saving the main group, clearing Mount Natagumo, gaining the trust of the Hashira, and orchestrating the series of events that included letting Akaza escape at the Mugen Train with false memories a few days earlier, he had finally accumulated a considerable number of points.
Fifty thousand points.
This was the hard threshold required to upgrade the Sasuke template from the "Mangekyō Sharingan stage" to the "Eternal Mangekyō Sharingan stage."
The Mangekyō Sharingan was undoubtedly powerful. Whether it was the black flames of Amaterasu, the shape manipulation of Kagutsuchi, or the absolute defense of Susanoo, each of them could easily overwhelm opponents in this world.
However, it had one fatal flaw—loss of vision.
Every use of Mangekyō ocular techniques caused irreversible damage to the optic nerves, accompanied by a piercing pain that seemed to reach the very marrow.
Frequent use of Susanoo placed an even heavier burden on the body, eventually leading to blindness.
In this world filled with unknown dangers, where he might even have to cross into other dimensions in the future, eyes that could go blind at any moment were clearly a massive time bomb.
The "Eternal Mangekyō Sharingan" was the key to completely breaking those shackles.
"System, consume 50,000 Dimension Points to upgrade the current template to the Eternal Mangekyō Sharingan stage," Rin ordered without the slightest hesitation.
[Ding! Command confirmed.]
[Deducting Dimension Points: 50,000.]
[Template upgrade initiated—Target: Uchiha Sasuke (Eternal Mangekyō Sharingan stage).]
As the cold mechanical voice echoed in his mind, an unprecedented surge of energy descended from the void and poured directly into Rin's body.
"Ugh—!"
Rin let out a low groan, his hands suddenly clutching the tatami mat beneath him.
This power was different from any previous enhancement.
It did not affect his muscles or bones. Instead, it went straight to his brain and eyes.
A cold, vast surge of dark Release chakra, as deep as an abyss, erupted within his optic nerves.
Pain.
An indescribable agony instantly flooded his eyes, as if thousands of red-hot needles were piercing and reconstructing the inside of his eyeballs.
This was the inevitable transformation that occurred when ocular power broke through its genetic limits and underwent a qualitative evolution.
In the original Naruto world, this transformation required transplanting the eyes of a sibling. Here, however, the system used pure high-level energy to forcibly bypass that step entirely.
Sweat instantly soaked Rin's back.
He clenched his teeth tightly, not letting out a single sound.
The pain lasted for a full five minutes before slowly receding like the ebbing tide.
In its place came a stream of energy as cool and soothing as a clear spring, forming a perfect cycle between his eyes and brain.
The faint fatigue and stinging pain that had lingered deep within his head after activating Susanoo earlier were completely swept away at this moment.
Phew~~
Rin exhaled a long breath of turbid air and slowly opened his eyes.
In the dark room, two crimson glows suddenly lit up, like a demon lurking in the night.
The pattern of his eyes had undergone a drastic transformation.
At the center of the pupil, the three sharp angles of a hexagram extended outward into razor-straight lines, while three interconnected tomoe patterns were perfectly embedded within the hexagram.
The perfect fusion of the Straight-Tomoe Sharingan and the hexagram.
The Eternal Mangekyō Sharingan.
Rin raised his hand and quietly gazed at his palm.
His vision was clearer than ever before.
Even the tiny dust motes floating in the air and the faint airflow moving through the corridor outside the door appeared perfectly clear under the gaze of these eyes.
What shocked him even more was the chakra surging within his body.
The qualitative evolution of his ocular power had directly caused the chakra within him to expand exponentially.
If his chakra had previously been like a rushing river, then now his inner world had transformed into a vast ocean.
"So this is what the Eternal Eyes feel like."
Rin focused his mind for a moment.
Buzz!
A cluster of pitch-black flames instantly ignited at his fingertips.
The black flames of Amaterasu radiated a terrifying heat, yet Rin did not feel even the slightest soreness or pain in his eyes.
With a flick of his wrist, the black flames twisted as if alive, changing shape freely at his command. One moment they formed a sharp blade, the next a long whip—Blaze Release: Kagutsuchi.
It moved like an extension of his own arm, without the slightest resistance, and more importantly, without any backlash.
Not only that, Rin could clearly feel that the power hidden deep within his pupils had been completely freed from its former restraints.
As long as he wished, he could summon at any moment that winged, dual-sword-wielding, godlike Perfect Susanoo capable of blotting out the sky.
In a world where the highest level of combat power was merely Kibutsuji Muzan, Rin, now possessing Perfect Susanoo, had truly reached a physical peak that could hardly be surpassed.
"Fifty thousand points, well spent."
Rin closed his fingers, and the black flames at his fingertips instantly vanished.
The complex patterns in his eyes slowly faded, returning to deep black pupils.
He pushed open the window, and the night breeze drifted in, carrying the faint fragrance of wisteria flowers.
Now that his strength had undergone a qualitative leap, whether Muzan sent an Upper Rank to test him or personally appeared, Rin had absolute confidence he could devour his opponent completely.
"The quiet days are about to end."
Rin looked at the crescent moon hanging in the night sky, a sharp smile curving at the corner of his lips.
At this moment, deep within the Infinity Castle, undercurrents must already be stirring.
Let the storm come even fiercer.
____
12 Advance chapters:Patreon/slept01