"You want to spar with me?"
Muzan's crimson eyes glimmered faintly beneath the moonlight as he studied his younger brother, who stood before him with uncharacteristic seriousness. Kakashi's expression was focused, solemn—
and from that alone, Muzan knew this battle couldn't be avoided.
He slipped off his black cloak and spoke calmly, though his tone carried a faint warning.
"At night, my power increases significantly. You'd better be ready."
Even when he wasn't trying, the aura emanating from him felt overwhelming—an ancient, predatory pressure that made the air itself seem heavier.
It wasn't arrogance; it was the natural dominance that came with his bloodline.
Under the pale moon, Muzan could feel the same primal thirst that once belonged to the Demon King—
a quiet hunger stirring within.
Kakashi, however, stood his ground.
He was already a capable genin—well-trained in the Three Basic Jutsu and other elementary techniques. It was no coincidence he was hailed as Konoha's brightest young genius.
Even when faced with the oppressive pressure radiating from his brother, Kakashi refused to retreat.
"Hmph! Don't underestimate me! Let me show you what a real ninja fight looks like!"
---
In the small courtyard of the Hatake household, the wind rustled through the trees as moonlight filtered through the branches.
Kakashi's eyes sharpened, and with a sudden burst of speed, he dashed toward Muzan.
Thanks to constant sparring with Guy over the past few weeks, his taijutsu had improved drastically. He even trained with weighted sandbags strapped to his body.
Had his kick connected with an ordinary person, it would have shattered bones outright.
Bang!
Muzan raised both arms to block. The impact forced him back several inches, his feet skidding across the dirt. A dull ache spread through his arms.
For a moment, he was caught off guard by the sheer force—but his body quickly adjusted.
"Not bad, Kakashi. That flying kick had real weight behind it. You've been training seriously."
Kakashi smirked, panting slightly.
"All thanks to you. And… it seems your body really has changed, brother."
He was genuinely happy, even in the middle of a duel. For years, Muzan's frail health had been a constant shadow over their family. Seeing him this strong—this alive—made Kakashi's heart lighter.
"Then it's my turn to get serious," he said, forming seals with his hands.
If Muzan's strength came from his mutated body, then Kakashi would rely on his skill—on ninjutsu.
But Muzan only smiled faintly. "A clever approach."
He didn't rush in. He stood perfectly still, analyzing Kakashi's movements. Ever since arriving in this world, he'd focused on learning chakra control and kunai throwing. This sparring session was the perfect chance to observe a real shinobi's combat rhythm.
"But… it's not flawless."
Kakashi had made one mistake—he hadn't hidden his breathing. Muzan's sensory ability could distinguish even the faintest life signatures.
It was an instinct inherited from his demon blood—one that would later rival the sensory prowess of Kakashi's own ninken.
"Behind me? No—!"
Bang!
Kakashi barely escaped by using Substitution Jutsu, reappearing behind a tree just in time to see Muzan's fist punch straight through the trunk.
He stared, stunned.
"You… how did you find me?"
He prided himself on stealth. Could Muzan see chakra flow—like the Byakugan of the Hyuga clan?
"Defeat me, and I'll tell you," Muzan replied smoothly.
Kakashi landed lightly—but before he could counter, Muzan was already upon him.
His punches came like a storm—swift, relentless, impossible to predict.
Kakashi staggered backward, barely managing to block. His stamina began to wane; he needed space.
He's too strong… That bloodline really enhanced his body.
In a flash, he used Substitution Jutsu again, swapping himself with a wooden log. With the distance gained, he pulled out several kunai and launched them in a precise spread, sealing Muzan's path of retreat.
"Going all out on your big brother, are you?"
Muzan twisted his body unnaturally, joints snapping out of alignment to avoid the incoming kunai. But before Kakashi could celebrate, the dislocated joints snapped back into place with a sickening crack.
His medical knowledge—born from his goal of becoming a medical-nin—let him manipulate his own bones and muscles mid-combat.
"You're one to talk!" Kakashi snapped. His hands were already swollen from blocking Muzan's blows.
Muzan chuckled. "Then let me show you something new… something born of my bloodline."
His crimson eyes gleamed.
"Blood Demon Art — Black Blood Thorns!"
From his forearms sprouted dark, vine-like spikes, twisting around him like a living storm.
Each thorn glimmered with a faint metallic sheen, and as they lashed outward, the stone tiles of the courtyard cracked and shattered beneath their strike.
Even Kakashi froze.
"What kind of power is that…?!"
He'd never faced someone with a Kekkei Genkai before.
If those thorns entangled him, his body would be shredded before he could break free.
He dodged with a Substitution Jutsu again, forming hand signs in midair.
"Fire Style: Fireball Jutsu!"
A roaring sphere of flame burst from his mouth, hurtling toward the swirling thorns.
But these weren't real vines. They were biological extensions—flesh and blood molded by Muzan's chakra into thorn-like weapons.
When the flames struck, he could feel each burn as a sharp pulse of pain—proof that the thorns were still part of him.
"So this is the power of ninjutsu," Muzan murmured, watching the fireball dissipate. "Gathering chakra and converting it into elemental energy… fascinating."
He didn't fully understand the flow of chakra through the seals yet—otherwise, he could have released a Fireball Jutsu of his own.
"Your little fire trick won't burn through my thorns, Kakashi. Surrender."
The thorns whipped together, crushing the Fireball in a burst of embers.
"Don't joke around, brother," Kakashi growled, though his voice trembled slightly.
He had five chakra natures in potential—but his young body couldn't sustain large amounts of chakra yet. The Fireball Jutsu was one of the few offensive techniques he could manage, and it hadn't even scratched Muzan.
He needed another plan—fast.
With limited chakra, he'd have to rely on the Three Basic Techniques and precise kunai work to turn the tide.
He threw several kunai in a wide arc. Muzan scoffed—until his senses caught something off.
That trajectory… no, that chakra signature—
The instant the kunai flew past him, one of them shimmered and shifted shape.
"Not bad," Muzan murmured approvingly. "You really are Father's son."
Kakashi had used a combination of Substitution and Transformation Jutsu, disguising himself as a kunai to slip past the storm of thorns.
It was a brilliant feint—
but Muzan's thorns reacted faster than his human mind.
In a heartbeat, the vines twisted upward and wrapped around Kakashi mid-air.
"Got you."
A puff of smoke burst as the thorns crushed his body—another Substitution Jutsu. But this time, Kakashi was out of chakra. He appeared a few feet away, breath ragged, covered in shallow cuts.
Muzan stepped forward, the thorns retracting into his arms.
"You've run out of chakra, little brother. You can't continue."
Kakashi's legs wobbled. His vision blurred from exhaustion.
"…You win, brother."
Under the moonlight, Muzan smiled faintly—not with mockery, but with quiet approval.
He could feel the faint pulse of pride beneath the monstrous blood in his veins.
Kakashi, though defeated, had fought like a true shinobi—cunning, disciplined, and fearless.
And for the first time in a long while, Muzan felt something he hadn't known since awakening his power—
a spark of warmth that reminded him what it meant to be human.