As for Yin and Yang Release "cores," these referred to Hii Kōri's envisioned locations for storing different chakra separately.
Generally, chakra within the body didn't exhibit attribute tendencies. It only gained corresponding attributes when using corresponding attributes or through deliberate manipulation—Yin and Yang included.
The Yang Release training method recorded in Hii Kōri's biological parents' notes essentially transforms less chakra into Yang Release chakra, strengthening physical constitution during circulation.
But while generating cursed energy through spiritual power, Hii Kōri realized: since two different energies—chakra and cursed energy—could coexist within the body, perhaps different chakra natures could too.
For the regular five natures, this might only save attribute conversion time, enabling faster ninjutsu release. But for Yin and Yang, the implications were entirely different.
Yin Release, sourced from spiritual energy, possessed the properties of "creating matter forms from nothingness."
Yang Release, sourced from physical energy, possessed the characteristic of "influencing all things through one's existence."
Though opposite in nature, their training methods share common ground. If such cores could be built and run, it would be equivalent to continuously circulating Yin and Yang Release training methods.
At first glance, this seemed an impossibly fanciful idea. From ancient times to the present, no one had ever simultaneously endowed chakra with different attributes.
Though "combination techniques" existed, these were either coordinated by multiple people or rapid sequential techniques through extreme hand speed.
The closest approach was various nature-based kekkei genkai.
For instance, the invincible Hashirama Senju's Wood Release was considered a Water + Earth hybrid. But essentially, this "created" an entirely new chakra attribute—not simultaneously endowed with dual attributes.
Yet Hii Kōri didn't believe this impossible.
As a former Black Flash experiencer and jujutsu sorcerer who'd mastered cursed energy core control, his grasp of energy flow needed no elaboration.
In fact, regarding "core creation," Hii Kōri had already succeeded.
Designing the spiritual energy source—the brain—as the Yin Release core, and the physical energy engine—the heart—as the Yang Release core, mixing less chakra in the Dantian and transmitting it to both cores, continuously injecting spiritual and physical energy to transform it into Yin and Yang Release chakra—this wasn't difficult for him.
Moreover, once cores accumulated sufficiently—like oil droplets gathered on soup surfaces—less chakra would spontaneously flow toward cores, transforming into Yin and Yang without his conscious control.
The current problem: how to run these two different chakra natures simultaneously.
Hii Kōri had seen "Yin–Yang Release" in manga. But such late-stage concepts never detailed principles. In this world, related records were equally sparse and vague—completely useless as reference.
Unlike puppet improvements or Water Release research, this bothered him long-term. Predictably, even years might bring no progress.
But wasn't that how research worked? Most great discoveries arose from improvisation and intuition.
Hii Kōri felt he lacked that single spark of inspiration.
"Speaking of which, that guy Rasa might be graduating early."
Thinking of kekkei genkai reminded Hii Kōri of that perpetually sour-faced redhead in class.
Recently discovered to have Lightning Release talent, he'd been taken under the Third Kazekage's wing.
By manifestation, kekkei genkai roughly divided into two types: nature combination types—mixing different chakra natures to create entirely new attributes—and "physical mutation" types—directly manifested in organs.
Nature-based kekkei genkai were mostly new attributes developed by exceptionally talented ninja themselves. Due to differing fusion ratios, even same-nature combinations might differ—even the same blood successor's manifestations varied.
But confirmed: once a new Mixed with chakra nature, this bloodline would be recorded in the ninja's genes and passed to descendants through bloodline.
The Third Kazekage's Magnet Release seemed like an innate ability. Judging by attributes, it was Wind + Lightning hybrid.
Still single, the Third Kazekage is apparently intended to teach the next generation kekkei genkai, inheriting his kekkei genkai. (Or possibly escaping paperwork through "teaching students"—not impossible.)
Either way, this demonstrated that the widespread claim "kekkei genkai can only be inherited through bloodlines via genes" was pure nonsense.
Hence occasional voices claiming nature-based kekkei genkai weren't "true" kekkei genkai—probably from physical mutation families.
Which made things even funnier. Shikotsumyaku aside, this world's eyeball-based kekkei genkai were hot-swappable—anyone could pop them out and install them on the spot, more convenient than USB drives.
Hii Kōri knew this was just expression. Actual use required adaptability and other conditions—mismatches brought side effects.
But anyone who'd seen the follow-up manga couldn't forget those scenes.
The stereotype was fixed.
Regardless, whether kekkei genkai or not, being learnable and detachable was better, right? Such convenient, useful things should be maximized.
Hii Kōri's Wind and Water chakra—in the Country of Water's Kirigakure—developed Ice Release, a famous kekkei genkai
Lately, he occasionally tried mixing these two natures, seeing if he could fuse Ice Release to pass the time.
"Ah... actually, I just got notified too. About graduating ahead of time."
But Hii Kōri's casual remark made Pakura guiltily avert her gaze.
"Misawa-sensei said an ninja's willing to be my mentor..."
***
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