"Then… let's begin, Sakumo-sensei."
Seiji raised Muramasa, drawing in a long, steady breath.
Up until now, the strongest opponent he had crossed blades with was Uchiha Hachiyo—but that jōnin had been a poor benchmark. His entire move set had been countered perfectly by Seiji's abilities. This man standing before him, however… Hatake Sakumo. A Kage-level shinobi, no dead weight, no excuses. A soul who could carry the battlefield on his shoulders even in the thick of a shinobi world war.
The tomoe in Seiji's Sharingan spun wildly, the crimson glow sharp as fresh blood. Muramasa answered his will, flaring with savage fire.
In the blink of an eye—A burning slash cut the air at an impossible angle, arcing straight toward Sakumo!
"So fast!"
Kakashi's eyes widened. Even straining every nerve to follow, he could only glimpse fragmented afterimages.
If he fought me seriously… I wouldn't even have the time to raise an Earth Wall.
His fists clenched tight. Shame burned hotter than the fire on Seiji's blade.
Is this what a real genius looks like?
"Clang!"
Sakumo's White Fang blade, wreathed in dense azure chakra, intercepted Muramasa with perfect precision.
Seiji narrowed his eyes. My speed is within his perception… I'm still a step slower. No wonder he's so calm. Fine then. Time to test power—not half measures, but everything.
Muscles coiled, chakra flooding his arms with monstrous precision. His Sharingan tomoe spun faster, weaving an illusion that clawed at Sakumo's mind.
"Brute Force Style: Tobirama–Izuna Fusion Art—Cleansing Slash!"
A strike born from Senju Tobirama's explosive strength, Izuna's flowing kenjutsu, and Seiji's own ocular genjutsu—perfected into a single killing stroke.
Deep within him, Tobirama muttered, annoyed, Pointless. My Senju-style blade work alone would crush a Hatake sword… A pause. Still… the brat pulled it together well. Damn troublesome technique.
But his irritation rang hollow. Even Tobirama couldn't deny what he'd felt—the harmony between Senju and Uchiha styles. Two clans that had torn at each other for a thousand years, their killing arts merging seamlessly. The irony stung like a fresh wound.
Steel screamed. Seiji's blade roared toward Sakumo's chest.
For just an instant, Sakumo's focus slipped under the genjutsu haze. A heartbeat late, White Fang surged to meet Muramasa's arc.
And then—Sakumo's expression faltered.
Muramasa's strength crashed down, crushing White Fang's guard. Chakra-fueled brute strength surged through Seiji's body, multiplying his power several times over. White Fang's defense buckled, Sakumo forced back as though the sword itself wanted to devour him whole.
Only a lightning-fast surge of chakra saved him. With a blur of movement, he twisted clear, Muramasa's edge carving just a hair's breadth from his body.
Blood spattered the ground.
A shallow but undeniable gash stretched across Sakumo's chest.
"Impossible…" Kakashi's voice cracked. "Father—Father got pushed back by Uchiha Seiji?!"
For as long as he could remember, no matter how desperately Kakashi trained, Sakumo had never once moved in their sparring. Every strike had been swatted aside casually, his father smiling like it was a game. Kakashi's dream had always been simple: just once, make Father take a step.
Now, before his eyes, Seiji had carved that step for him.
Seiji exhaled slowly, lowering Muramasa. That was everything I had… brute force, ocular illusion, swordsmanship fused into one blow.
Against an elite jōnin, against even someone like Hachiyo, that would've been a clean kill.
But Sakumo Hatake had survived.
"Incredible. Truly incredible, Seiji-kun." Sakumo glanced down at the blood staining his chest, smiling lightly. "Lucky you're still a child. If you had an adult's body behind that swing… I might be the one needing a medic."
Seiji shook his head. Age was an excuse—one he refused to cling to. In the shinobi world, only those who survived to adulthood mattered. A "genius" who died before then was just another wasted name.
"Please don't hold back, Sakumo-sensei," Seiji said, eyes burning. "I want to see what someone like you is truly capable of. I know a little medical ninjutsu—I'll survive. Just leave me one breath."
His tone was serious, unyielding.
Sakumo studied him in silence, then murmured:
"…You have a pure heart, Seiji-kun. If I kept refusing, that would be arrogance."
In that moment, Sakumo's presence shifted. His aura sharpened like a blade unsheathed, the air itself turning hostile. Just looking at him made one's eyes sting, one's neck prickle cold.
Then—
Sakumo raised White Fang. An immense wave of chakra-infused sword energy howled forth, tearing the battlefield into scorched ravines, hemming Seiji in from all sides.
And Sakumo himself? He vanished into a blur, White Fang's edge concealed, waiting—like death itself—for the one fatal opening.
Hatake Sakumo had stopped holding back.
Later, after the ground had been carved to blackened ruin, Kakashi whispered, "Father… did you go easy on him?"
Sakumo shook his head. "The opposite. I was serious."
"Right now, Seiji-kun can't beat me head-on. But… if he relied on genjutsu and water release, it'd be nearly impossible for me to keep him pinned."
He rested a hand on Kakashi's shoulder. "Work hard, Kakashi. You've met a peer who's a true prodigy."
Yet, in Sakumo's eyes, there lingered a trace of pity.
Because deep down, he didn't believe Kakashi would ever surpass Seiji.
Every generation of shinobi bore a single, monstrous genius—one so far above their peers they might as well be a mountain none could climb.
And Sakumo knew. Uchiha Seiji was that mountain.