Nobibei spared no effort in teaching everything he knew about chakra control. Having once served under Sakumo Hatake in the White Fang's squad, he saw this as a way of repaying Sakumo's past kindness.
During these lessons, Muzan made an unexpected discovery—
his chakra reserves were abnormally vast.
Balancing spiritual and physical energy, the two sources of chakra, posed no difficulty for him at all.
His demonic physiology granted him powerful regenerative abilities and an incredibly active body, while his reincarnated soul strengthened his mental energy severalfold beyond ordinary humans.
"Such an enviable talent…"
Nobibei couldn't help but sigh.
All afternoon, he'd been training Muzan to control the tiniest threads of chakra—guiding leaves through the air, balancing energy output. Yet even after hours, the boy's chakra flow remained steady and tireless.
"Honestly," the teacher muttered, shaking his head, "comparing people like this just isn't fair."
When he finally glanced at the clock, it was already the end of class. Another day of his peaceful semi-retirement had passed.
"Alright everyone, that's enough training for today!"
For the average Academy student, afternoon sessions on throwing weapons were little more than playtime—few had the discipline or coordination to make progress.
---
Just as Nobibei exited the Academy gates with Kakashi and Muzan, a commotion caught their attention.
A man in a green jumpsuit was bowing repeatedly, almost in tears.
"Please, Mr. Matsushita! I'm a shinobi too! My son can mold chakra—I swear he can!"
It was Might Duy, the eternal genin.
Desperate and humiliated, he pleaded for his son's future. He didn't want Guy to end up like him—a man mocked as a failure.
Becoming a ninja was his son's only dream, his only chance.
"I've told you a hundred times already," Matsushita snapped. "Your boy can't become a ninja! He doesn't have chakra!"
The official yanked his arm free, glaring irritably.
Were it not for the fact they stood before the Academy's gates, he might have thrown Duy off the grounds entirely.
Watching this unfold, Muzan immediately recognized both faces.
So, it's them… Might Duy and Might Guy.
A faint smile crossed his lips. Didn't expect to meet true future legends this early.
"You… know that man?" Nobibei asked, surprised.
Given Muzan's noble background, he'd expected him to associate with geniuses, not failed shinobi.
Seeing Muzan's interest, Nobibei stepped forward to intervene.
"Hey! What's going on here?"
Matsushita froze mid-stride, realizing with dread that he'd just been caught by another instructor.
Great. There goes my promotion.
He turned and pointed at Duy in frustration.
"Mr. Nobibei! This man's son can't perform ninjutsu or generate chakra. He has no place in the Academy!"
Duy didn't get angry. Instead, he clenched his fists and spoke with rare determination.
"My son works incredibly hard. I know he'll become a great shinobi one day!"
Even Kakashi, standing nearby, was drawn to the exchange.
Everyone knew what it meant when a child couldn't extract chakra properly: they were a defective case.
After the Second Great Shinobi War, genin had been little more than cannon fodder. Konoha later restricted admissions, refusing to take in students with poor chakra potential.
And Might Guy, by every measurable standard, was one of those "defective" children.
"This is… complicated," Nobibei sighed.
He'd seen parents like this before—ordinary people who believed love and effort could overcome the cruel arithmetic of talent.
But for most, the price was tragedy:
a lifetime stuck as a low-rank shinobi, or a meaningless death on some forgotten mission.
Muzan's gaze, however, lingered on Guy—his jaw clenched, his fists trembling with resolve. His chakra might be weak, but his spirit burned bright.
Muzan stepped forward and placed a hand on the boy's shoulder.
"Why not use what you do have?" he said quietly. "Being a shinobi isn't only about chakra."
Everyone turned toward him, startled by the calm authority in his voice.
Guy's eyes welled with tears. Overcome, he threw his arms around Muzan.
"Thank you! I'll prove that taijutsu can be just as powerful!"
Muzan smiled faintly, then looked toward Nobibei.
"Teacher, this afternoon you said that when chakra runs out in battle, a shinobi must rely on kunai. So… why not give him a chance to demonstrate?"
Under Muzan's steady gaze, Nobibei hesitated.
Then, catching a glint of crimson from beneath the boy's hood, he nodded.
"…Very well. Show us your taijutsu."
Thud! Thud!
Two loud impacts echoed across the training field, kicking up clouds of dust.
Both Nobibei and Kakashi stared, stunned.
"I underestimated him," the teacher admitted. "Truly… not bad at all."
"What insane physical strength," Kakashi murmured. "Even most adults couldn't handle weights like those!"
Guy shed his heavy training weights, and his movements instantly blurred with explosive speed.
Each punch tore through the air; his dodges were sharp and precise.
Even an Academy graduate would struggle to match him.
When his demonstration ended, Nobibei suppressed his astonishment.
To find such potential right at the school gates was rare indeed.
His taijutsu fundamentals were flawless—given the right training, he could one day reach special jōnin, maybe higher.
"With that level of skill," Nobibei declared, smiling, "you can enter the Academy.
From this day forward, you're officially a student of Konoha Ninja Academy."
Cheers erupted.
Father and son embraced tightly, tears streaming down their faces.
Around them, bystanders shivered at their sheer enthusiasm.
"This… this is the flame of youth!" Duy shouted, voice breaking.
"My youth will burn ever brighter!" Guy echoed with equal passion.
Muzan ignored their theatrics. What caught his attention was Kakashi—whose usual dead-fish eyes now shimmered faintly with emotion.
Until now, among all the new students, no one had surpassed him in anything.
But watching Guy's relentless spirit shook something inside him.
If it were me, Kakashi thought, could I train with such weight on my body every single day?
"Don't overthink it, Kakashi," Muzan said softly.
"You're both geniuses—just in different ways."
He patted his younger brother's shoulder encouragingly, recognizing the fire in his eyes.
Muzan made a silent vow then and there—he would never let Kakashi become the Copy Ninja bound by another man's eye.
For all his brilliance, Kakashi's future was marred by limits:
his chakra reserves weren't small, but the Sharingan he would later inherit from Obito would drain him constantly, crippling his potential.
Mastering all five chakra natures meant little when one's energy was being devoured every second.
He'd be better off mastering the Hatake Sword Style, Muzan thought. Carrying on Father's legacy as the next White Fang.
Or perhaps specializing in advanced Konoha ninjutsu—after all, as the future Fourth Hokage's student, Kakashi would have access to the Third Hokage's personal archives.
He could even become a true "Ninjutsu Professor" one day.
"Tsk," Kakashi muttered, recovering his pride.
"A guy without chakra can train all he wants—he'll never catch up to me."
Muzan chuckled.
"You'd be surprised, little brother."
He turned to Guy, who was still bawling joyfully and pulled him closer.
"Guy, from today onward, I want you to challenge Kakashi regularly. Show him that hard work can rival genius!"
---
The Green Beast of Konoha was born that day.
Even now, Muzan wondered if Guy might already possess the strength to open the Eight Gates.
"Damn you, brother!" Kakashi yelled in protest, face twitching.
Muzan only smiled, his crimson eyes glinting under the shadow of his hood.
"Competition's good for you. After all… this village could use a few more hard-working geniuses."