First, there was the "rejuvenation" of his mindset.
Although "live and learn" is a broad consensus in human society, statistically derived data actually yields the conclusion that "the golden period for human learning is from birth to youth"—completely opposite to "common sense."
Of course, such statistics might be unfair if applied to the Naruto world. After all, until just over forty years ago, the average life expectancy for ninja in this world hadn't exceeded thirty. Civilians far from the battlefield might have fared slightly better, but still couldn't expect to surpass forty.
Without even a widespread existence of "old people," talk of "learning until old" was even more irrelevant.
But considering only physiological and psychological factors, humans indeed have the most active thinking, the highest receptivity, and the strongest comprehension when young.
As a researcher, experience accumulation was certainly extremely important, but that "light" mindset belonging to youth was undoubtedly even more crucial.
Not being confined by past experience, occasional flashes of inspiration, sparks of creativity from life's details... these were abilities that those who increasingly became steadfast, increasingly difficult to stir, increasingly sinking into hopeless senility, could never possess.
Hii Kōri was someone who believed in the romance of research and could truly appreciate its charm. Treating research as a pleasure, he never wanted to lose that lightness of heart.
Because the pursuit of pleasure should itself be endless.
A firm and pure will was a form of power, and Yin Release was the means to forge that will into a blade.
If you so desire, you shall receive a powerful response.
On the other hand, there were the real negative effects.
Just as Hii Kōri had gained Wind and Water nature transformations due to his soul's strong inclinations, Yin Release had probably solidified his understanding of "energy systems" onto his body.
Of course, of course. He knew being bound by previous life knowledge was foolish, but some things, even when recognized, were difficult to change.
Subconscious cognition, amplified by suddenly strengthened Yin Release, then affecting the body—even Hii Kōri hadn't anticipated this.
His current treatment method was to rely on chakra suppression bandages wrapped around his entire body to slow Yin Release chakra's circulation efficiency, while simultaneously using cursed energy to shield external influences, allowing Yang Release chakra to operate normally, attempting to pull Yin and Yang back into balance.
Chakra suppression bandages were originally developed by him to pair with "Tenketsu Unlocking Technique"—a medical ninjutsu that temporarily opened chakra points through external stimulation to adjust physical condition.
By partially blocking chakra circulation, the amount of chakra released by the Tenketsu Unlocking Technique could be controlled within a smaller range. Through subtle adjustments paired with his computational ability, he could suppress chakra flow throughout his entire body.
Ironically, his Yin Release had gone berserk because he achieved triple-layer divided thinking, and now the solution also came from the further increased computational ability from divided thinking.
Within seven steps, the antidote is always found.
As for the reason he couldn't learn Lightning Release...
The Five Elements, the Seven Luminaries, the Four Elements theory... none of the elemental interaction cycle systems Hii Kōri had encountered in his past life included "Lightning" as a basic element.
From an occult perspective, lightning was regarded as fire from heaven. From a physics perspective, lightning was caused by charge separation from collision and friction of small suspended particles.
Starting from the former, lightning would be induction under an extension of fire. Starting from the latter, it was generally regarded as derivative of wind. Not to mention in the Eight Trigrams system, the Zhen trigram was attributed to wood.
But regardless, lightning itself was never included as a fundamental element in cyclical systems.
Moreover, although Hii Kōri was someone who wanted to toy with mathematical statistics, he had to admit that many things in mathematics couldn't be denied by sheer passion alone.
Mathematics cannot prove its own correctness using mathematics; Within the same system, one can only prove "non-contradiction." Gödel's Incompleteness Theorems were clearly not limited to mathematics but possessed universality elsewhere.
Especially after he could already use Earth, Water, Fire, and Wind nature transformations to construct a simple cycle, the existence of the Lightning attribute became even more subtle.
Like, bro, why are you even here?.
Even now, he sincerely believed this. So learning Lightning Release would obviously have to wait until his Yang Release balanced with Yin Release again, eliminating Yin's negative effects.
"Ha, I never understand the stuff you say, kid."
Many abilities in this world were used vaguely even by their users—like the Uzumaki Clan's Adamantine Sealing Chains, or Shukaku's own Magnet Release.
As a talented player, the big-tailed tanuki had never understood Hii Kōri's rambling principle explanations. But not understanding didn't matter; Shukaku just liked listening to Hii Kōri chat.
He didn't understand Bunpuku's sutra chanting either, but that didn't stop him from liking Bunpuku—same principle.
"Kōri, new intelligence has arrived."
The door to the maintenance room slowly opened and Pakura's tall, slender figure emerged, handing Hii Kōri a stack of intelligence reports.
Seeing this, Shukaku jumped down from Hii Kōri's lap, vaulted over the railing and ran off towards the outer levels.
Clearly, the ensuing conversation would be nothing more than repetitive nonsense about war and plans—something he had heard countless times before. The big-tailed tanuki had no interest in any of it.
"Mm... doesn't seem worth reading..."
Casually flipping through a couple of pages, he tossed the stack of detailed records documenting each nation's recent movements onto a nearby table. Hii Kōri grasped Pakura's wrist and pulled her into his embrace.
"These are clearly important intelligence, aren't they? With careful analysis, you could always find something useful."
Sitting on her lover's lap, Pakura had long grown accustomed to this level of contact. After all, the three of them had already done everything they should and shouldn't do.
"Mmm... for modern intelligence agencies, the trouble has never been lack of intelligence, but rather too much information obtained through various channels—in fact, if you predicated the timing of war outbreak at any point from the beginning of the year to now, you could always shoot the arrow first and then draw the target, finding corresponding intelligence to support that view."
Arms wrapped around his lover's waist, his face buried in her bare back, Hii Kōri marveled at how chakra had remarkable effects on softening skin while elaborating his philosophy in a muffled voice.
Just as a certain British intelligence officer after WWII said: "In the twenty years between 1919 and 1939, we received a lot of intelligence every year about the imminent outbreak of the next world war, and we were wrong only once."
"Besides, all the preparations we could make are already done. What we're waiting for now is just notification from the Daimyō..."
"Is that so?"
"After all, if we're to strike first, we need to choose a suitable season."
Just as Hii Kōri judged in that moment, two months later, Sunagakure—having received instructions from the Daimyō—officially declared war on Konoha.
The same year, Iwagakure also announced its entry into the war.
Konoha Year 38: The Second Shinobi World War began.
***
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