Setsuna didn't know whether the complex entanglement spanning centuries between Zaraki and Unohana had been resolved, but the present fact was that Zaraki's swordsmanship skill was skyrocketing at a terrifying pace.
This wasn't surprising. Zaraki's innate combat talent had already reached an astonishing level.
The combat experience he had accumulated over centuries, enough to fill mountains of corpses and seas of blood, was an incalculably vast treasure.
This experience had long been integrated into his very marrow, becoming the most primal yet most lethal component of his wild swordsmanship.
Now, having had his direction pointed out by Setsuna, he began systematically contacting orthodox swordsmanship concepts and frameworks with a mindset of 'learning in order to break'.
The effect could be described as a dimensionality reduction strike.
It was like a maverick genius who, relying on astonishing intuition and original methods, had already won the highest honor in mathematics, the [Fields Medal], then turning back to systematically study the axioms, theorems, and deductive systems of basic mathematics.
Those theories, arcane and obscure to ordinary people, were often grasped instantly in his eyes. He could even immediately see through their essence and limitations, and naturally integrate and verify them with his own, more grand or unique system.
And Unohana, serving as his primary sparring partner and 'encyclopedia of traditional swordsmanship' at this stage, went by the name [Yachiru], signifying mastery of all known swordsmanship and Zanjutsu schools throughout Soul Society's history, past and present.
In less than a month, Zaraki had learned roughly seventy to eighty percent of the essence of the vast and deep swordsmanship styles Unohana demonstrated.
He didn't imitate mechanically, but devoured this knowledge in a wild yet efficient way: watching, sparring, feeling, understanding, and then interpreting and even distorting them with his own fierce and uninhibited combat style.
Unohana's ever-changing sword techniques, containing endless killing intent, were often simplified and strengthened in Zaraki's hands, becoming more direct, heavier slashes and thrusts more in line with his instinct. But their core 'principle' and 'momentum' were precisely captured and absorbed by him.
Through this high-intensity, high-level swordsmanship training and confrontation, Zaraki actually began to gain a faint comprehension of Ultra Instinct.
Although still far from truly entering that mysterious realm of 'consciousness separation, body autonomous', occasionally during fierce combat, he indeed experienced a moment or two of nearly 'acting before thinking', using ultimate combat intuition to resolve lethal crises.
It wasn't deliberate, resembling more the natural sublimation of his vast battle instinct under extreme pressure, resonating to some extent with the concept of Ultra Instinct.
Witnessing all this, Setsuna couldn't help but inwardly marvel: 'Zaraki Kenpachi's talent was truly unfairly strong. Perhaps he is born a monster meant solely for battle.'
But that was good. As his own strength continuously increased, only Zaraki could keep pace with him.
He needed opponents to push himself beyond his limits in terms of Reiatsu.
If, in the original work, Aizen transcended the boundary between Shinigami and Hollow to surpass 1st-Class Reiatsu, then Setsuna planned to first surpass 1st-Class Reiatsu, and then use the power of a Shinigami and Hollow who had already surpassed 1st-Class Reiatsu to break that boundary.
Therefore, he needed opponents to help him transcend himself.
…
Within the training ground's barrier, figures of gold and crimson wildly interwove and collided at speeds barely perceptible to the naked eye.
The roar of Reiatsu was like a continuous rumble of thunder. The explosive clashes of blade against blade seemed capable of shattering space itself.
Dust, gravel, severed Reishi Currents… all formed the fierce backdrop of this battle, surpassing ordinary Captain-level combat.
Zaraki's wild laughter and roars barely ceased. Every strike carried the violent power to split mountains and evaporate seas.
Setsuna, however, stood like a reef standing amidst the storm, using supremely refined body movement and his gradually maturing realm of [Ultra Instinct - Omen] to resolve the other party's unreasonable fierce attacks.
This level of high-intensity combat had already lasted an entire month.
After another fierce exchange of Zanpakuto against hand-sword, the two separated by dozens of meters, propelled by the force.
Zaraki's body was marked by numerous fresh wounds, but his eyes grew brighter, his battle intent burning like tangible flames.
He didn't immediately pursue. Instead, he stood still, slightly lowering his head, breathing heavily. His battered Zanpakuto hung at his side, its tip lightly touching the ground.
Suddenly, the fierce boiling Reiatsu around his body underwent a bizarre change.
It didn't calm, nor did it strengthen. Rather, it became restrained and took on a peculiar rhythm.
The Reiatsu, which had been violently fluctuating due to the intense battle and excited emotions, began to stabilize in a way that defied common sense. It even achieved a certain synchronization with his breathing, heartbeat, and even the micro-tremors of every muscle.
Then, the restrained Reiatsu erupted abruptly, clinging to his body like an invisible armor, forming a visible, slightly rippling silver-white Reiatsu Halo.
His movements instantly became incredibly natural and efficient, as if every minute adjustment conformed to some universal truth, yet perfectly matched his wild combat style.
"Hey! I did it!" Zaraki roared with joy, his voice filled with unparalleled sense of achievement and excitement.
Before the words faded, the ground beneath his feet exploded, and his figure vanished from the spot.
The next instant, he appeared before Setsuna. His Zanpakuto, carrying a silver-white light trail more condensed and more unpredictable than ever, cleaved down towards Setsuna's head.
This slash was fast, precise, and fierce! And it carried a sense of 'naturalness', as if the blade was destined to appear at that time and place.
More crucially, as he delivered this strike, the joy expression on Zaraki's face didn't diminish at all. That boiling battle intent and emotion not only failed to interfere with his movements, but seemed instead to become fuel driving this 'autonomous' body.
'What?' Setsuna's pupils contracted. He swung his arm to block.
Clang!!!
Setsuna felt his arm go numb. His body was actually forced back a step by this strike, which combined ultimate power with 'autonomous' technique. The ground beneath him cracked deeply under the force.
'He's suppressing me instead,' Setsuna's mind shook. After entering the [Ultra Instinct - Omen] realm, Zaraki's power increase far exceeded expectations.
It wasn't just speed and reaction, but a qualitative change in combat efficiency and threat level.
'And, despite being in a state of intense joy, with his Reiatsu fluctuating due to emotion, the 'Ultra Instinct' state didn't collapse. Could it be that what he comprehended is an Emotional Omen?'
'As expected of Zaraki, always able to forge his own path,' Setsuna inwardly mused.
At the same time, he was incredibly excited, 'Finally, someone could make me feel pressure.'
The two continued fighting, the pressure Zaraki applied growing ever greater.
Finally, the Reiatsu within Setsuna, which had long reached its tipping point and only lacked a final push, advanced under this ultimate external pressure and the catalysis of his own continuously strengthening battle intent.
Like a dam bursting, rivers flowing backwards.
A surge of Reiatsu, far purer, vaster, and more condensed than before, erupted from the depths of Setsuna's soul.
A golden Reiatsu Pillar uncontrollably shot into the sky, stirring the clouds above the training ground into a vortex.
The surrounding space slightly twisted under this pressure, emitting a strained hum.
1st-Class Reiryoku!