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The laboratory had grown silent, save for the steady pulse of chakra from the sealing arrays etched across the walls. It had been four months since Kirito last pushed himself into isolation. Four months since he ordered his clones into unending drills, experiments, and combat simulations.
In that silence, his power had reached new heights.
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The Seal of a Hundred
The first breakthrough came from the forbidden scrolls of Konoha, where he had copied and studied the medical texts associated with Senju Tsunade.
The Strength of a Hundred Seal was no mere technique. It was a reservoir of chakra, gathered meticulously over years and released when needed, amplifying healing and physical performance beyond limits. For most, mastering it would take decades.
But Kirito had an advantage. His chakra core allowed daily infusion of condensed chakra into a seal etched into his forehead with fuinjutsu precision.
For months, he sat cross-legged in meditation, compressing and sealing chakra into the growing diamond mark. The mark shimmered faintly with restrained power, pulsing in harmony with his core.
With my core feeding the seal, I don't need decades. I need discipline, precision, and patience, he thought, as the final layer of sealing script locked into place.
He tested it once—activating a partial release. The result was instantaneous: his body surged with strength, fatigue vanished, and chakra healing accelerated rapidly.
So this is Tsunade's secret… but I have made it mine.
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Creation Rebirth
But the Strength of a Hundred was incomplete without its crown jewel—Creation Rebirth.
By manipulating mitotic acceleration, Kirito's body could heal wounds instantly at the cost of cellular life span. With his clones' relentless practice, he found a balance: by linking his regeneration to the seal, he could offset the dangerous drain by infusing chakra steadily instead of recklessly burning his life away.
A blade cut across his palm. Flesh knitted instantly, not a scar left behind. His chakra core pulsed, replenishing what was lost.
Immortality? Not quite. But near-limitless endurance in battle—an edge no shinobi can rival.
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Spirit Transformation Technique
The next technique was far more insidious—Spirit Transformation Technique, a forbidden jutsu that separated the user's soul from the body, allowing possession or assassination of enemies directly.
It was risky. A single mistake would leave the body defenseless, the soul vulnerable.
But Kirito prepared. He wove fuinjutsu barriers to protect his comatose form, stationed clones as guardians, and practiced slipping his spirit into animals first—birds, foxes, stray cats in the forest.
The experience was disorienting, yet exhilarating. He could fly, slither, or stalk silently. With more practice, he learned to suppress his spiritual signature, masking his presence even from trained sensors.
An assassin's art… but mine will not be so crude. With clones guarding my body and marks ready for teleportation, this technique will become an unseen blade.
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The Path of the Eight Gates
The most grueling of his new pursuits was the Eight Gates.
The forbidden technique forced the body to break its limits by forcibly opening the chakra gates that restrict life energy. Most who trained in it died from the strain. But Kirito had his chakra core, his seal-enhanced healing, and the Strength of a Hundred to back him up.
For four months, he tested himself against his limits:
Gate of Opening: Enhanced speed, reflexes, and stamina. He mastered it within weeks, weaving it into taijutsu sparring with clones.
Gate of Healing: Accelerated recovery during combat. Combined with Creation Rebirth, fatigue became irrelevant.
Gate of Life: His body glowed green, strength surging explosively. His clones struggled to match his strikes.
Gate of Pain: His muscles tore under the force, yet healed instantly under his seal's regeneration.
Gate of Limit: His chakra roared violently, elemental jutsu magnified. His fire release became storms, his lightning release crackled like a thunder god's roar.
He pushed no further—for now. The Fifth Gate was dangerous enough, and he needed more time to test the synergy between the gates and his regeneration.
Still, he knew. If he mastered all Eight Gates with his sealing and healing to support him—he could rival legends.
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The Integration
On the final day of his four-month training, Kirito stood in the center of his lab. Dozens of clones surrounded him, their hands weaving seals, lightning sparking, elemental chakra swirling.
He opened the Fourth Gate—muscles surging with power, speed blurring his form. At the same time, he activated the Strength of a Hundred Seal, flooding his body with reserve chakra.
Chidori crackled in his palm, but instead of a single strike, he funneled it into a multi-point release, five clones mirroring him. Explosive tags layered seals across the battlefield, detonating in perfect synchrony with his attacks.
Above, a clone activated the Spirit Transformation Technique, slipping from its body and striking at seals hidden in the walls.
The lab was chaos, yet every movement was controlled, orchestrated by his mind.
He deactivated the gates, released the seal, and let silence return. His body healed instantly, fatigue erased by regeneration.
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Reflection
Kirito placed a hand over his chest, feeling the chakra core pulse steadily. His forehead burned faintly with the Strength of a Hundred Seal, a symbol of his new mastery.
Four months… and I have stepped beyond what even the Sannin dared to grasp. Healing, strength, possession, forbidden gates—all mine. The world will never see me coming until it is too late.
He sat back, issuing orders to his clones to continue experimentation. Tomorrow, he would test these abilities outside the lab—in missions, in battle, in the real world.
For now, he closed his eyes. The hum of power filled the chamber. The storm he was becoming was not yet unleashed—but soon.
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