"Itachi… Uchiha Itachi."
Sasuke's voice was low, almost conversational, but each syllable dripped with a venom that no seven-year-old throat should have been capable of producing. The Mangekyō Sharingan spun lazily in his crimson eyes — six-pointed stars rotating like the gears of some terrible, beautiful machine — as he stared at the spot where his brother had stood just a heartbeat ago.
"Do you have any idea how pathetic you are?"
The words hung in the blood-soaked air of the Uchiha main house, heavy and sharp, aimed to wound in ways that no blade ever could.
In that same instant — the exact moment the accusation left Sasuke's lips — Itachi completed his Body Flicker. He materialized behind Sasuke in a blur of displaced air and shadow, his hand already descending in a precise knife-strike toward the base of the boy's neck. It was a textbook ANBU takedown. Silent. Efficient. Merciful.
But Sasuke was already turning.
The scarlet six-pointed stars of his Mangekyō locked onto Itachi's figure the instant he appeared — no, before he appeared. Those terrible eyes had tracked the vector of Itachi's movement through the Body Flicker itself, reading the displacement of air molecules and the subtle shifts in thermal energy that preceded his materialization. By the time Itachi's hand reached for the pressure point, Sasuke was already facing him, already looking up at him with those blood-red eyes and that wicked, knowing smile curling at the corners of his small mouth.
Itachi's eyes widened fractionally. Then understanding dawned.
"I see," he murmured, his voice carefully measured despite the spike of surprise that lanced through him. "The Sharingan's perception — you read the hand signs of my Body Flicker before I completed the jutsu. You saw my movements and reacted before I even arrived." A pause. His eyes narrowed. "But being able to see an attack and being able to do something about it are very different things. Don't overestimate yourself, Sasuke."
Sasuke's response was not words.
"Die."
The single syllable cracked through the air like a gunshot.
Before Itachi could draw another breath, Sasuke moved.
A terrifying force erupted from beneath Sasuke's feet — not chakra, not in any way Itachi recognized — but something rawer, more fundamental. The boy's small body manipulated the kinetic vectors of the ground itself, redirecting the earth's reactive force upward and forward through his legs in a single, perfectly calculated burst. The tatami mats beneath his sandals cratered. The floorboards splintered.
And Sasuke vanished.
He didn't use the Body Flicker Technique. He didn't weave a single hand sign. He simply redirected every vector of force acting upon his body — gravity, friction, air resistance, the kinetic energy stored in his own muscles — and converted them all into pure forward momentum.
The result was speed that defied comprehension.
This was not the speed of a shinobi. This was not the speed of a seven-year-old, or a Genin, or even a Jōnin. This was the speed of Accelerator — the Number One Level 5 esper of Academy City — filtered through a child's body and amplified by the computational assistance of the Mangekyō Sharingan's perceptive processing.
Fast.
Impossibly, unreasonably fast.
Faster than Itachi had anticipated. Faster than the Body Flicker Technique that had just carried him across the room. The air itself screamed in protest as Sasuke's small frame tore through it, leaving a vacuum wake that sucked the blood-spattered paper doors inward with a violent rattle.
Before Itachi could react — before the genius prodigy of the Uchiha clan, the ANBU captain who had massacred his entire family in a single night, could so much as blink — Sasuke was behind him.
The six-pointed stars of the Mangekyō blazed in the darkness, reflected in Itachi's widening eyes like twin red suns.
A small foot swung toward the back of Itachi's head.
A child's kick. Tiny. Seemingly harmless.
Itachi saw it coming. Even caught off-guard, his reflexes were those of a Kage-level shinobi honed by years of life-or-death combat. His Mangekyō Sharingan tracked the trajectory of Sasuke's leg with perfect clarity. His body was already responding — muscles coiling, weight shifting, one hand rising to intercept.
"You've surprised me more than once tonight," Itachi said, his voice betraying a complex swirl of emotions — pride, sorrow, bewilderment — that flickered across his usually impassive features like shadows cast by a guttering flame. "But your body is still too small. Too weak. Your physical strength is that of a child, Sasuke. No matter what you've awakened, that fundamental limitation hasn't changed."
His hand reached out to catch Sasuke's kick — casually, almost gently, the way an older brother might deflect a younger sibling's playful swing.
But Sasuke's grin only widened.
That smile — too sharp, too savage, too old for the face wearing it — stretched across his features like a crack spreading through glass. His Mangekyō blazed brighter, the six-pointed stars spinning so fast they became solid rings of crimson fire.
"Underestimating me," Sasuke whispered, "comes at a price."
Itachi's fingers closed around the incoming ankle. Contact.
The force was small. Negligible, even. The physical strength behind the kick was exactly what Itachi had predicted — the meager output of a seven-year-old's underdeveloped musculature. Nothing that could threaten him. Nothing worth worrying about.
A faint, sad smile crossed Itachi's face.
"Foolish little brother," he began, his tone settling back into the cold, rehearsed cadence of the role he had chosen to play. "The Mangekyō is not invincible. Tonight, I'll teach you that in the face of absolute power—"
"Oh," Sasuke interrupted, his voice silk-smooth and dripping with dark amusement. "You've been fooled."
The blood-red six-pointed stars in Sasuke's eyes exploded into violent rotation.
And then the world came apart.
Vector Manipulation.
The principle was devastatingly simple. Every physical phenomenon in the universe could be described as a vector — a quantity possessing both magnitude and direction. Force. Velocity. Heat transfer. Electrical current. Air pressure. Even the kinetic energy contained within a seemingly harmless child's kick.
What Accelerator's ability did was rewrite those vectors.
At the point of contact — at the precise instant Itachi's palm touched Sasuke's ankle — the super-brain processor embedded deep within Sasuke's neural architecture performed a calculation of staggering complexity in a fraction of a microsecond. It analyzed every vector passing through the point of contact: the kinetic energy of the kick, the thermal energy radiating from skin against skin, the reactive force of Itachi's grip, the ambient air pressure, even the faint electrical impulses running through Itachi's peripheral nerves.
And it reversed them.
No — it didn't merely reverse them. It amplified them. It gathered every scrap of kinetic energy within a three-meter radius — the residual force of Sasuke's movement, the stored potential energy of the surrounding air, the vibrational energy of the floorboards, the thermal differential between the warm interior and the cold night outside — and compressed it all into a single, focused point.
Then it released everything. All at once. Directly into Itachi's body.
The Mangekyō Sharingan's computational power served as a secondary processor, supplementing the super-brain's calculations with its own pattern-recognition capabilities. It was an imperfect synergy — Sasuke's young brain lacked the neural development to run the super-brain at anything close to full capacity, and using the Mangekyō as a computational crutch placed an enormous strain on his optic nerves. Blood was already seeping from the corners of his eyes, tracing thin scarlet lines down his cheeks like crimson tears. His body screamed in protest, every cell burning with the agony of channeling forces that a child's frame was never designed to contain.
But against Itachi — against a single, unsuspecting opponent who had just willingly grabbed the point of contact — it was more than enough.
The detonation was instantaneous.
A shockwave of compressed kinetic and atmospheric energy erupted outward from the point where Itachi's hand met Sasuke's ankle. The air itself seemed to solidify for a split second — a perfectly spherical, transparent distortion expanding from the impact point like a glass bubble inflating at impossible speed — before it burst with a sound like thunder cracking inside a sealed room.
BOOM.
The concussive force was apocalyptic.
Every window in the Uchiha main house exploded simultaneously — not outward, but inward first, sucked toward the vacuum created by the energy compression, before the shockwave reversed direction and blew them apart in a hailstorm of shattered wood and glass. The paper walls disintegrated. The ceiling beams cracked. The tatami mats were ripped from the floor and hurled against the far walls like ragdolls.
And Itachi —
"Gah—!"
A fountain of blood erupted from Itachi's mouth. His eyes — the legendary Mangekyō Sharingan of Uchiha Itachi, the eyes that had cast Tsukuyomi and bent reality to their will mere moments ago — went wide with naked, undisguised shock. The force that slammed into his body was nothing like a child's kick. It was nothing like any jutsu he had ever encountered. It was a pure, mathematical redistribution of energy — cold, precise, absolute — and it hit him with the force of a small building collapsing onto a single point.
His body was lifted off its feet and hurled backward like a broken marionette. The wooden wall behind him didn't slow him down — he tore through it, sending planks and splinters spraying into the night air. The next wall met the same fate. And the next.
My dear brother, Itachi thought, his consciousness flickering as blood filled his mouth and the world blurred past him in a kaleidoscope of shattered wood and dark sky, when did you become...
In the final fraction of a second before impact, instinct overrode disbelief. Itachi's Mangekyō blazed, and with the last dregs of his concentration, he activated the only defense that could save him.
Susano'o.
The air around his tumbling body ignited with a deep, fiery crimson light. Ethereal bones materialized from nothing — a massive skeletal ribcage wrapping around his torso, spectral arms extending outward, a half-formed skull flickering into existence above his head. It was the first stage of Susano'o — the skeletal frame, incomplete and unstable — manifested in desperation rather than deliberate intent.
It wasn't enough.
The shockwave caught up to him. The compressed energy — still expanding, still carrying the full, redirected payload of every vector Sasuke had gathered — slammed into the skeletal Susano'o like a battering ram striking a wall of glass. The spectral bones shuddered. Cracks spiderwebbed across their surface. The ethereal ribcage held for precisely one-point-three seconds before it buckled, fractured, and shattered into wisps of dissolving crimson chakra.
Itachi crashed into the street outside.
The impact carved a crater into the packed earth — five meters wide, two meters deep — sending up a plume of dust and debris that billowed into the smoke-choked sky. The sound was thunderous, rolling through the empty streets of the massacred Uchiha district like the dying echo of a war drum.
Itachi lay at the bottom of the crater, his Susano'o gone, his body broken and bleeding. His ANBU armor was cracked in three places. Blood poured freely from his mouth, his nose, the corners of his eyes. The Mangekyō Sharingan still spun in those eyes, but sluggishly now — dazed, unfocused, struggling to process what had just happened.
What… he thought, staring up at the crimson-stained sky through a haze of pain and dust. What in the world was that?
He had fought Kage-level opponents. He had sparred with shinobi who could reshape landscapes with a single jutsu. He had faced down the full might of the Uchiha clan's finest warriors and cut them down without breaking stride.
None of them — none — had ever hit him like that.
"My dear brother," he whispered, blood bubbling on his lips, the words barely audible. "It seems… when I wasn't looking… you've already…"
He couldn't finish the sentence. Another convulsion wracked his body, and he coughed up a thick spray of crimson that spattered across the cracked earth.
Ten meters from the crater's edge, hidden in the shadow of a partially collapsed house, a figure in a spiral-patterned orange mask stood perfectly still.
Uchiha Obito had seen many things in his life. He had watched his childhood crush die on his best friend's hand. He had stood before Madara Uchiha himself and accepted the mantle of his twisted legacy. He had manipulated the Nine-Tails into attacking the Hidden Leaf Village and watched the Fourth Hokage die sealing the beast. He had orchestrated wars, toppled nations, and danced through dimensions with Kamui.
He had never — not once in his entire existence — seen anything like what he had just witnessed.
He knew the Mangekyō Sharingan. He possessed the Mangekyō Sharingan. He understood its power intimately — the cost, the capability, the limitations.
He knew Itachi's strength even better. He had personally recruited the boy, had fought alongside him during the massacre, had watched him cut down elite Jōnin and hardened clan warriors with the cold efficiency of a surgical instrument. Uchiha Itachi at thirteen, wielding the Mangekyō Sharingan, was a Kage-level combatant by any reasonable metric. One of the most dangerous shinobi alive.
And he had just watched a seven-year-old blast that Kage-level combatant through three houses and into a crater deep enough to bury a horse.
With a kick.
Obito raised one hand and slapped himself across the face. Hard. The sharp crack of palm meeting mask echoed in the stillness.
I'm awake, he confirmed. This is real. This is actually happening.
He took a slow, deliberate breath and forced his racing pulse to steady.
What the hell is that child?
Not far ahead of him, partially concealed behind the ruins of a collapsed fence, a young girl watched the scene unfold with wide, terrified eyes. She was beautiful in the fragile, delicate way of the Uchiha — fine-boned, dark-haired, her pale skin smudged with ash and streaked with tears. She couldn't have been older than Sasuke.
And in her eyes — spinning wildly, driven to frantic rotation by the sheer overwhelming terror of what she was witnessing — blazed the fully matured three-tomoe Sharingan.
Obito noted her presence with cold, clinical interest, then dismissed her. She was irrelevant to the immediate situation. What mattered was the monster standing in the wreckage of the Uchiha main house, the boy with the Mangekyō Sharingan and the impossible power that didn't obey any rule of ninjutsu that Obito had ever encountered.
In the crater, Itachi spat another mouthful of blood onto the broken ground.
His entire body trembled. Not from the cold. Not from chakra exhaustion. From something far more fundamental — the deep, marrow-level shudder of a body that had been struck by a force it could not comprehend. Every bone ached. Every organ throbbed. The skeletal Susano'o had absorbed perhaps thirty percent of the impact before shattering, and the remaining seventy percent had passed directly through his body like a wave of pure destruction.
What is happening? The thought echoed through his fractured consciousness, looping, spiraling, finding no purchase. Has the world gone mad? Am I dreaming? Is this a nightmare?
If it was a nightmare, he wanted desperately to wake up.
Because none of this made sense.
Sasuke was seven years old. He had been attending the Academy for barely two years. He hadn't even graduated. He hadn't completed a single mission. He was supposed to be a promising but ultimately normal child — talented, yes, carrying the blood of the Uchiha, yes, but fundamentally a child. A child who should have been cowering on the floor, broken by the Tsukuyomi, traumatized into the precise emotional state that Itachi's plan required.
Instead, that child had awakened the Mangekyō Sharingan — a feat that should have been physiologically impossible at his age — and then proceeded to launch an attack that had shattered Susano'o and nearly killed a Kage-level shinobi in a single blow.
I am Uchiha Itachi. The thought was almost plaintive in its disbelief. I am the strongest genius the Uchiha clan has produced in a generation. I graduated from the Academy at seven. I awakened the Sharingan at eight. I became a Chūnin at ten. I joined ANBU at eleven. I am thirteen years old and I fight at the level of a Kage.
On what grounds does Sasuke — my seven-year-old little brother who hasn't even learned to properly mold chakra — have the power to do THIS to me?
The question echoed unanswered through the smoking ruins of the Uchiha district.
Another convulsion ripped through his chest. He doubled over in the crater and vomited a fresh spray of blood, his vision swimming, his thoughts fragmenting.
One kick.
A single kick from a seven-year-old child had very nearly killed him outright.
If he hadn't activated Susano'o in that final instant — if his instincts hadn't screamed loud enough to override his paralyzed disbelief — that blow would have pulverized his internal organs. He would have died in the street, surrounded by the corpses of the clan he had just massacred, killed by the little brother he had been trying to save.
The irony was so savage it almost made him laugh.