Although the Shinigami in the current Seireitei all practiced the same Kidō, as long as their Reiatsu was sufficient to fully release a specific spell, the effects and power were largely identical.
However, when it came to Kidō training and the sensation of releasing it, most Shinigami experienced it differently. For instance, when Kōe released Kidō, it felt as though an invisible pen was tracing distinct patterns across an endless white scroll in his mind. Yet, both Urahara and Yoruichi stated they felt nothing of the sort.
Therefore, innate talent in Kidō training was paramount. Every nine levels of Kidō represented a minor breakthrough. Even among spells of similar power within the same tier, one might find themselves completely clueless about a specific one.
Of course, this wasn't an issue for Kōe's trio. Even for Yoruichi, whose primary combat method was Hakuda, any Kidō below the eighties posed no problem whatsoever.
Besides, the Kidō required for Shunkō wasn't overly complex. It wasn't like high-level Hadō such as [Hadō #90・Kurohitsugi], which required gathering highly concentrated Reiatsu from a distance and possessed binding, defensive, sensory-obscuring, and primary severing properties.
What Shunkō required was very simple: condensing Reiatsu and detonating it. The true difficulty lay in how to minimize the reaction time as much as possible, transforming Kidō—which normally required conscious thought to activate—into something as instinctual as wielding her Zanpakutō.
Indeed, even when Kōe cast the lowest level [Hadō #1・Shō] right now, he still had to trace the pattern in his mind. The so-called incantation-less casting was merely familiarizing oneself with the sensation of releasing the Kidō to the absolute limit, eliminating the need for a spoken chant to assist the process.
Kōe, however, possessed a unique talent akin to having two souls. This granted him incredibly powerful perception, allowing him to drastically reduce the casting time and barely enabling him to use Kidō on the fly during close-quarters combat.
But Yoruichi's requirements went a step further than that. Taking Kōe as an example, even for a purely explosive Kidō, different concentrations of Reiatsu required different patterns to be drawn. A tiny variation meant the resulting Kidō was entirely different.
Yoruichi's goal was to conjure a Kidō with identical Reiatsu from absolutely nothing the exact moment she was struck by an incoming Kidō, perfectly canceling it out. Coupled with the fact that Shunkō essentially involved point-blank combat, this meant her brain's processing speed had to match her body's subconscious reaction speed. Making the conscious equal to the subconscious—no matter how you looked at it, it was a harsh demand.
However, Yoruichi's words gave Kōe an inspiration. Could continuous stimulation force Yoruichi's body to automatically form muscle memory, making the Kidō developed for Shunkō infinitely close to a zero-reaction-time cast, or even an instinctual reflex?
Specializing in Hakuda, Yoruichi's physical reactions were incredibly fast. Kōe had once conducted an experiment where the two stood shoulder-to-shoulder and threw punches at each other's faces.
Without any prior warning and without focusing his attention entirely on Yoruichi, Kōe could only manage to grab her wrist, still taking a punch to the face. Yoruichi, on the other hand, could completely block his fist.
If they could truly reach a point where Yoruichi's body automatically mobilized Reiryoku to release the corresponding Kidō, then within a three-step radius, Yoruichi would be an invincible existence.
Even if it fell slightly short and only allowed her physical perception to trigger a subconscious Kidō release, a close-combat Yoruichi would absolutely be a nightmare for any enemy.
It was just that this training, compared to Yoruichi's previous regimens, was simply hellish. Right now, in the underground cavern, Kidō ranging from numbers one to eighty-nine were being fired from Kōe's hands, attacking Yoruichi from every conceivable angle. The cavern was constantly illuminated in a myriad of colors, creating a deceptively beautiful spectacle.
But for Yoruichi, who was on the receiving end, the only color she saw was the red of her own blood. A proper Kidō battle was indeed nothing like their previous minor skirmishes. Even with Kidō below level seventy, whose Reiatsu she was already familiar with, Yoruichi's probability of perfectly canceling them out didn't exceed fifty percent.
Yoruichi had already lost count of how many times her arms had been scorched or sliced open. This bone-deep, agonizing pain showed no signs of diminishing, no matter how many times she experienced it.
If it weren't for the black robe she was wearing, Yoruichi felt she might have given up by now. Relying solely on Urahara's hot spring to fully adapt to these Kidō would take an unimaginable amount of time.
The black robe Yoruichi wore was naturally Kōe's Bankai, Kōki Rakusen'i. Without an ability like Static Recording, Kōe truly wouldn't have the heart to torture Yoruichi like this.
However, the immortal robe also had a flaw: it couldn't train her back. Regarding this, Kōe expressed that muscle memory should be universal across the body. Even if it wasn't, she could just wear the robe backward later to specifically train her back. It wasn't a big deal.
Static Recording could record the body's physical state, but it did not include memories or muscle memory.
Although this method couldn't enhance her physical attributes, trying to resist Kidō with just the physical body was too fantastical anyway. Besides, Yoruichi's physique was already infinitely close to the absolute limit a Shinigami could achieve; no matter how much stronger she got, there wouldn't be any breakthrough changes.
What Yoruichi needed was muscle memory, and of course, the ability to rapidly judge subtle shifts in Reiatsu. Achieving either of these would be enough to support her in executing Shunkō.
To ensure Yoruichi could truly react to various Kidō on the fly, Kōe not only drastically varied the levels of consecutive spells, but he would also shout "Hadō #13" while actually firing Hadō #30, or even a Bakudō. This was to minimize the effectiveness of Yoruichi's mental anticipation.
Not only that, but Yoruichi's development of Shunkō wasn't limited to the registered ninety-nine Hadō and Bakudō; it encompassed all Kidō-like attack patterns.
To break Yoruichi out of her fixed mindset, Kōe would also cast some original Kidō he had developed himself, occasionally using spells that interacted with one another.
For example, he would first cast [Bakudō #7・Freezing Rain] [Original Kidō], then quickly sweep [Hadō #4・Byakurai] through the falling raindrops, creating a cloud of white mist that possessed both freezing and paralyzing properties.
The introduction of these little tricks made Yoruichi suffer even more. Judging the Reiatsu of such combined Kidō wasn't as simple as one plus one. Sometimes, the Reiatsu contained in these combinations was lower than either of the individual spells, yet the resulting effect rivaled high-level Kidō.
The previous training had indeed caused Yoruichi to fall into a somewhat rigid way of thinking. It was like taking a test where she had seen all the questions before; although she tried her best to suppress it, she still slipped into relying on past experience to solve the problems.
Now, that sense of familiarity was ruthlessly shattered. As the training continued, Yoruichi actually managed to rediscover a bit of the joy she felt when she first practiced Hakuda. Her initial lack of confidence vanished. She was now certain that with Kōe's help, the day Shunkō was perfected would inevitably arrive.
And Kōe wasn't just a sparring partner. As the training progressed and Yoruichi rapidly improved, the sessions gradually shifted toward a true mock battle, which was equally significant for Kōe.
Although he was extremely skilled in Kidō, truth be told, most of the Kidō Kōe had developed remained in the theoretical stage. How to apply them in actual combat relied mostly on mental simulations.
Now, having a Captain-class individual as his sparring partner—especially a top-tier assassin like Yoruichi, who posed the greatest threat to those who primarily used Kidō for offense—Kōe benefited immensely.
Overly idealized Kidō had to be refined or even discarded. His casting techniques became increasingly proficient, and most importantly, he gained new insights into Kidō without the need for secluded meditation.
Kōe even somewhat rediscovered the original joy he felt when he first dabbled in Kidō—that feeling from his past life of writing code, as if he were personally creating a world with his own hands.
So, a person's gains and losses were truly unpredictable. Hakuda and Kidō would one day merge, and Kōe and Yoruichi—a pair of rivals who bickered whenever they met—could one day tangibly open up new worlds for each other.
These days continued without much interruption, until one day, two years later, a single sentence brought by Urahara caused the situation to turn strange.
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