The temperature in the deep mountains plummeted drastically as night fell, a freezing contrast to the humid heat of the day. Shinnō, wrapped tightly in a thin woolen blanket, leaned against the trunk of a massive oak tree. His eyes were closed, but sleep completely eluded him.
Normally, a man who had spent decades wandering the continent as a solitary, rogue physician would have long since adapted to the harsh conditions of the wilderness. He shouldn't be suffering from insomnia. But tonight, a suffocating, inexplicable dread gripped his chest. His instincts screamed that a catastrophy was rapidly approaching him.
Suddenly, the silent, deadly whoosh of displaced air cut through the ambient noise of the forest.
Shinnō's eyes snapped open. Though his hair and beard were stark white, betraying his advanced age, his physical reflexes were terrifyingly explosive. He violently threw himself to the side, the lethal steel of a thrown kunai embedding itself deep into the tree trunk exactly where his skull had been resting a fraction of a second prior.
Rolling smoothly to his feet, Shinnō dropped into a defensive stance, his eyes locking onto the dense underbrush at the edge of the clearing. "Why did you initiate an ambush?" he demanded, his voice projecting a flawless, wounded innocence. "Is there some sort of misunderstanding? I am merely a traveling physician."
The brush parted. Kei Hyuga stepped out into the moonlight, leaning heavily on his iron-tipped cane.
"It was remarkably difficult to track your whereabouts, Shinnō," Kei noted, a warm, conversational smile plastered across his face.
Even utilizing Pakkun's legendary olfactory tracking, Kakashi and Kei had spent two grueling days chasing phantoms. It was only when Kei expanded his sensory web to its absolute maximum radius that they finally managed to isolate the doctor's erratic chakra signature.
Shinnō eyed the blind youth with deep, paranoid wariness. His gaze instantly locked onto the blue fabric tied around Kei's forehead. "A Konoha shinobi," Shinnō murmured, his innocent facade cracking slightly. "What exactly does the Leaf want with an old doctor?"
"I have heard magnificent rumors regarding your unparalleled medical expertise," Kei replied, taking a slow step forward. "I have traveled a great distance to beg for your clinical assistance in curing my blindness."
Shinnō's eyes glinted with calculation. "Is that so? Please, step closer into the light. I must conduct a preliminary ocular assessment."
"Of course. Thank you for your benevolence," Kei nodded gratefully. He began to shuffle forward, leaning heavily on his cane, projecting the absolute vulnerability of a crippled civilian.
As Kei closed the distance, a sickening, predatory smile slowly stretched across Shinnō's weathered face.
When the gap between them closed to less than five meters, the frail old doctor vanished. Shinnō pushed off the dirt with Jonin-level kinetic force, lunging at Kei with the terrifying speed of an apex predator.
Mid-lunge, a hidden, razor-sharp surgical blade slipped from Shinnō's sleeve into his grip. He aimed a lethal, upward thrust directly at Kei's heart.
However, in the exact millisecond before the steel pierced his chest, Kei moved. With blinding, effortless speed, Kei swung his cane upward, parrying the thrust flawlessly.
CLANG!
The sharp shriek of metal colliding with iron echoed through the silent forest.
Utilizing the kinetic recoil of the parry, Kei executed a light, graceful backflip, landing securely at the edge of the clearing.
Shinnō landed in the dirt, his surgical blade vibrating in his hand. He stared at the blind doctor, a flicker of genuine, bitter disappointment crossing his eyes. The easy kill had evaporated.
"Shinnō," Kei asked, his voice adopting a tone of hurt confusion. "I am merely a desperate patient seeking your holy healing. Why would you attempt to murder me?" Kei tapped a finger against his hitai-ate. "Are you truly unafraid of triggering a violent retaliation from Konoha?"
Shinnō let out a harsh, barking laugh, dropping the benevolent physician act entirely. "The Hidden Leaf owes the Sky Village a massive, unpaid blood debt. I haven't even begun to collect what is owed. But since you were foolish enough to deliver yourself to my doorstep, I will gladly collect a small down payment of interest tonight."
As he spoke, Shinnō dropped his center of gravity, his face twisting into a mask of undisguised, fanatical killing intent. The kindly, selfless saint the villagers worshipped was gone; the man standing in the clearing was a ruthless, hardened butcher.
Watching the transformation, Kei did not even flinch. He simply turned his head slightly toward the dark treeline behind him.
"Well, Captain Kakashi," Kei called out cheerfully. "I believe the conditions of our wager have been satisfied. You may start your assault now."
Kakashi stepped out from the shadows of a massive oak tree. He stared at Shinnō, his visible eye wide with a complex mixture of shock, anger, and profound embarrassment.
"Although he initiated hostile action," Kakashi argued stubbornly, refusing to concede the bet entirely. "That does not definitively prove your psychological profile was accurate. He simply harbors a grudge against Konoha regarding the Second Shinobi War."
"Kakashi, your stubborn refusal to accept cerified data is truly staggering. It is a severe cognitive defect," Kei sighed, shaking his head. "I sincerely hope you maintain that exact same level of denial when the bill for your wager comes due."
Kei's smile returned, cold and sharp. "But for now... please fulfill the duty of your bodyguard commission and apprehend this terrorist."
Seeing the terrifying, confident smile on the blind man's face, Kakashi felt a sudden, familiar spike of unease. He realized instantly that Kei had completely manipulated him into a corner. By forcing him to act as the executioner, Kei had guaranteed he would win the wager.
But Kakashi had no time to argue the semantics of the bet.
In the center of the clearing, Shinnō was undergoing a horrifying, impossible biological metamorphosis. The frail, wrinkled skin of the old man rapidly expanded as massive, roped muscles bulged across his entire body. His stark white hair and beard darkened instantly, turning pitch black.
What truly suprised Kakashi, however, was the sudden, suffocating explosion of chakra erupting from Shinnō's newly weaponized physique. It was not normal shinobi chakra. It was thick, vile, and radiated a pure, concentrated aura of malice.
"Ninja Art: Super Revival Fist!"
The moment Shinnō registered the presence of the infamous Copy Ninja, he realized holding back was suicide. He instantly channeled the massive reserves of Dark Chakra he had spent decades harvesting into his palm.
The energy condensed into a swirling, highly unstable sphere of dark purple particles—a bastardized, malicious imitation of the Rasengan. With a single, crater-forming stomp, Shinnō crossed the clearing instantly, driving the dark sphere directly toward Kakashi's chest.
"Earth Style: Mud Wall!"
Kakashi's hands blurred through a sequence of seals. A massive, thick earthen barricade, adorned with the carved faces of his ninken, erupted from the soil directly in Shinnō's path.
BOOM!
The collision generated a deafening explosion, kicking up a massive cloud of dust and pulverized rock.
As the smoke cleared, the reality was revealed. The heavy earthen wall was severely cracked and spider-webbed, but it had successfully absorbed the kinetic impact. Shinnō had been forced to retreat several paces, his expression grim.
He was intimately aware of Kakashi Hatake's lethal reputation. That was precisely why he had immediately deployed the Dark Chakra he had spent a lifetime stockpiling. However, seeing the ANBU captain flawlessly block the strike, Shinnō realized standard combat ability were insufficient to secure a victory.
Kakashi glanced at Kei, who was standing casually on the periphery. "You do not seem remotely surprised by the physiological mutation or the anomalous chakra signature. What classified intelligence are you withholding?"
"That is Dark Chakra, Kakashi," Kei answered, adopting the tone of a university lecturer. "It is a highly volatile energetic compound synthesized entirely from intense, concentrated negative human emotion."
"Shinnō has spent the last decade traveling the continent, operating under the guise of a benevolent healer. In reality, he has been utilizing his medical practice as a front to systematically harvest the despair, agony, and terror of the dying."
"He is stockpiling this Dark Chakra to fuel a specific, apocalyptic project. Once he secures a physiologically viable host vessel, he intends to utilize the energy to artificially synthesize a Tailed Beast: the Zero-Tails."
"Considering the Sky Village's fanatical hatred for Konoha," Kei concluded smoothly, "I calculate I do not need to outline what he intends to do with a weapon of mass destruction once it is operational."
Kakashi instantly understood the implications. His visible eye hardened into absolute, lethal focus. If Kei's intelligence was accurate, allowing Shinnō to survive the night was an unacceptable threat to village security.
Kei had not bothered to lower his voice. Hearing his highest-level, absolute state secrets casually broadcast across the clearing, Shinnō's pupils constricted to pinpricks.
"You miserable brat..." Shinnō hissed, genuine panic bleeding into his voice. "How could you possibly possess intelligence regarding the Zero-Tails?!"
"You infiltrated the Leaf and stole the foundational scrolls detailing the forbidden jutsu formula," Kei replied simply. "Did you honestly believe the ANBU Black Ops were entirely ignorant of your petty theft?"
"I see," Shinnō murmured. His panicked expression abruptly smoothed out into a mask of cold, absolute resolve. "While I cannot fathom how a blind cripple deduced my operational timeline, it is ultimately irrelevant. The dead do not file intelligence reports."
The Zero-Tails had not yet secured a perfect human vessel, and exposing the entity before the integration was complete risked catastrophic failure. However, he had no alternative. These two Leaf shinobi had to be eradicated tonight.
With a roar of effort, Shinnō fully unlocked the internal seals suppressing the Dark Chakra within his core. He violently activated the Zero-Tails jutsu formula.
If he were solely facing Kei, Shinnō would never have risked deploying the incomplete beast. But facing Kakashi Hatake required absolute, overwhelming force.
As the forbidden formula flared to life, a massive, horrifying entity tore its way out of Shinnō's physical body. It was a colossal, undulating mass of dark purple shadow. The beast vaguely resembled a massive python, but its skin was entirely smooth and devoid of scales.
As a synthetic, artificial Tailed Beast, the creature's 'face' was a flat, featureless white mask bearing the kanji for 'Zero' (零). Four long, red tendrils of hair floated eerily from the top of its mask, and a singular tendril hung from its chin. The aesthetic was deeply unsettling—simultaneously comical and terrifyingly oppressive.
Standing on the edge of the clearing, Kei 'stared' at the monstrosity with profound, clinical fascination.
He had orchestrated this entire tracking mission for two highly specific objectives.
The primary objective was the acquisition of Shinnō's Body Revitalization Jutsu. The medical technique possessed the theoretical capability to force absolute, rapid cellular regeneration. It was the absolute prerequisite for repairing his necrotic optic nerves and resurrecting his Byakugan.
The secondary objective was the Zero-Tails itself.
In a purely functional sense, the Zero-Tails was a drastically weakened, synthetic imitation of a true Bijuu. While it lacked the apocalyptic, continent-shattering power of the Nine-Tails, it possessed a massive tactical advantage: the Zero-Tails lacked higher cognitive sentience. It possessed no ego to rebel against its host. It was entirely subservient to the will of its Jinchuriki.
If Kei could successfully harvest the beast and bind it to his own chakra network, it would act as a massive, self-replenishing external battery. The influx of Dark Chakra would exponentially elevate his current physical lethality, bridging the gap toward Kage-level power.
Merging his consciousness with the beast, Shinnō initiated the assault. The massive, smooth body of the Zero-Tails violently split open, erupting into dozens of thick, muscular, whip-like tentacles.
The vast majority of the tentacles surged toward Kakashi, attempting to crush the primary threat, while a smaller cluster whipped toward the blind doctor.
Reacting with flawless ANBU instinct, Kakashi drew a kunai and channeled wind-natured chakra into the blade, slashing violently at the incoming appendages.
To his shock, the steel simply bounced off. The seemingly soft, shadowy flesh of the tentacles possessed an extreme, rubbery resilience that completely negated the slashing damage.
Facing the incoming cluster of tentacles, Kei did not retreat. He calmly raised a single hand and formed a specific tiger seal.
Phantom Body Flicker!
In a fraction of a millisecond, dozens of flawless, solid afterimages of Kei materialized across the clearing. The clones moved in perfect, chaotic synchronization with the original body, instantly flooding the battlefield and completely confusing the beast's targeting algorithms.
Because Shinnō had devoted the majority of the beast's processing power to suppressing Kakashi, the few tentacles assigned to Kei thrashed wildly, entirely incapable of isolating the true doctor among the swarm of phantoms.
"Stop conducting baseline diagnostics, Kakashi!" Kei shouted as he blurred across the clearing. "Use your highest-lethal jutsus immediately! You serve as the primary attacker; I will provide tactical interception!"
Kakashi did not hesitate. He reached up, tearing his hitai-ate upward to expose the blazing red tomoe of his Sharingan. Simultaneously, his hands blurred through a complex sequence of seals.
Instantly, Kakashi's right hand was engulfed in a concentrated, violently sparking sphere of high-voltage lightning. The iconic, deafening sound of a thousand chirping birds filled the forest.
Kakashi dropped his center of gravity and accelerated rapidly, utilizing his Sharingan to perfectly predict and dodge the thrashing mass of tentacles. As his kinetic velocity peaked, the penetrative power of the Chidori reached catastrophic levels.
Sensing the lethal, incoming threat, Shinnō desperately commanded the Zero-Tails to construct a dense, interlocking wall of tentacles in front of its main body to intercept the strike.
Kakashi completely ignored the barricade. He channeled all his kinetic momentum into a single, devastating thrust, driving his arm straight through the mass of tentacles and burying the Raikiri deep into the central mass of the Zero-Tails.
Deep within the core of the beast, Shinnō's physical body was instantly flooded by the high-voltage electrical discharge. The agonizing shock violently disrupted his nervous system, severely crippling his control over the synthetic Bijuu.
Seizing the micro-second opening, Kei and his swarm of phantoms leaped simultaneously into the air, landing perfectly on the sprawling back of the Zero-Tails and sprinting rapidly toward the creature's masked head.
Through the haze of electrocution, Shinnō sensed the fatal threat approaching his blind spot. He frantically rerouted all of the beast's power, commanding every single tentacle to instantly converge on its own back to crush the doctor.
The Zero-Tails thrashed violently, its massive body convulsing like a dying snake as a dozen heavy tentacles slammed down onto its own spine with bone-crushing force.
However, utilizing the absolute, untraceable evasion of the Phantom Body Flicker, Kei flawlessly swapped his physical position with his afterimages, dancing effortlessly through the chaotic barrage of strikes without suffering a single scratch.
Standing below the beast, Kakashi watched Kei's maneuver with absolute, staggering disbelief.
That is Shisui Uchiha's signature jutsu! Kakashi's mind screamed. How the hell did a Hyuga acquire the Body Flicker?
Before Kakashi could process the impossibility, he witnessed a second thing that completely shattered his reality.
As Kei closed the distance to the beast's head, the blind doctor raised his right hand.
Chidori!
A blinding, perfectly concentrated sphere of blue lightning erupted in Kei's palm, screaming with the exact same, deafening frequency Kakashi had just utilized.
As the creator and sole practitioner of the technique, Kakashi's brain completely short-circuited. How the hell does he possess my jutsu?!
Furthermore, based on the pure acoustic frequency and the violent concentration of the chakra, Kakashi realized with horrifying clarity that Kei's proficiency with the Chidori was absolutely identical to his own. It was a flawless, one-to-one replication.
Seeing the doctor casually deploy his life's work, Kakashi felt a bizarre, infuriating sense of violation. It felt as though Kei had reached into his skull, stolen his deepest secrets, and was now mocking him with them.
While Kakashi wrestled with his outrage, Shinnō was currently experiencing an infinitely more agonizing reality.
Kei drove his Chidori directly through the white porcelain mask of the Zero-Tails, burying his hand deep into the beast's core and making direct physical contact with Shinnō's actual skull.
A catastrophic, high-voltage surge flooded Shinnō's brain. The rogue doctor and the Zero-Tails convulsed simultaneously in a violent, synchronized seizure, nearly electrocuted to death instantly.
In a final, desperate bid for survival, Shinnō attempted to force the beast into a massive death roll to dislodge the doctor, but his paralyzed nervous system refused to respond.
With Shinnō's control entirely severed, Kei grabbed the rogue doctor by the collar of his robes, violently ripped his charred, smoking body completely out of the core of the Zero-Tails, and slammed him brutally into the dirt.
Shinnō hit the ground hard, his muscles spasming uncontrollably. He braced his blackened, trembling hands against the soil, desperately attempting to channel chakra to activate his Body Revitalization Jutsu to heal the massive cellular damage.
He was absolutely unwilling to accept defeat. If his masterpiece had been fully complete, a mere ANBU captain and a blind cripple could never have breached his defenses!
However, before he could mold a single fraction of healing chakra, Kei stepped forward and crushed his heavy boot directly down onto Shinnō's hands, shattering the metacarpal bones and instantly terminating the jutsu.
Looking up at Kakashi's lethal silhouette standing nearby, and the blind, smiling doctor standing over him, Shinnō realized with absolute, horrifying clarity that his survival chance had dropped to zero.
"I curse you!" Shinnō shrieked, his voice bubbling with blood and pure, venomous hatred. "You miserable, blind cripple! You will die in the dark! You will never regain your sight!"
Facing the dying man's desperate curse, Kei simply tilted his head, adopting an expression of mild, clinical pity.
"You are a truly pathetic person, Shinnō," Kei murmured, his voice cold and analytical.
"You spent the vast majority of your life cowering in the shadows. You orchestrated complex, continent-spanning espionage to steal the jutsu formula. You spent a decade harvesting the despair of the dying to fuel your masterpiece. You were standing on the very precipice of absolute success..."
Kei leaned closer, his dead eyes staring directly into Shinnō's panicked face. "And then, you had the misfortune of encountering me."
"The singular, crowning achievement of your entire, miserable existence has been effortlessly dismantled. As for those pathetic Sky Ninja remnants eagerly waiting for you to return with their salvation... rest assured, I will eventually hunt them down and exterminate them as well."
Kei gestured with his cane toward the massive, paralyzed body of the Zero-Tails resting nearby. "Furthermore... you intended to cultivate this entity to serve as your apocalyptic weapon, did you not?"
"I have excellent news for you," Kei smiled, a terrifying, demonic curve stretching across his face. "After I terminate you, I am going to use your corpse as the fertilizer to complete the beast's development. And then, I am going to bind it to my own soul."
"Everything you bled for, everything you sacrificed for, everything you built... now belongs entirely to me. Not even the grave will grant you an escape from my utility."
Kei tilted his head again, asking a final, surgical question. "Your life's work has been reduced to my personal stepping stone. Are you satisfied with your diagnosis?"
Shinnō's mind entirely fractured. The absolute, unmitigated horror of the scenario Kei had just painted—the realization that his very soul and his masterpiece would be enslaved and utilized by his murderer—completely broke his remaining sanity.
"Devil!" Shinnō shrieked, his voice tearing, his eyes wide with pure, unadulterated madness. "You are a devil!"
Overwhelmed by a sudden, catastrophic surge of psychological terror and rage, Shinnō's heart violently gave out. He vomited a massive gout of black blood onto the dirt, convulsed once, and died instantly of sheer fright.
Simultaneously, a mechanical chime echoed clearly in Kei's mind.
[Psychological treatment successfully concluded. The patient's psychological defenses experienced total, catastrophic collapse, resulting in sudden cardiac arrest induced by profound psychological terror. Degree of Mental Perturbation: Superb.]
[Based on the clinical treatment results, you have obtained: Body Revitalization Jutsu & The Zero-Tails Jutsu Formula.]
[Note: Body Revitalization Jutsu: An S-rank, highly classified medical ninjutsu engineered by Shinnō. Upon absolute mastery, the technique forces the user's cellular matrix to rapidly regenerate, exponentially elevating physical lethality, durability, and enabling recovery from otherwise fatal trauma.]
[Note: Zero-Tails Jutsu Formula: The forbidden, foundational fuinjutsu required to synthetically generate, command, and securely integrate the Dark Chakra entity known as the Zero-Tails.]