Chapter 36: Kekkei Genkai
As for the 'cores' for Yin Release and Yang Release, this referred to Hiiro Rinko's theoretical concept of storing different Chakra types in separate locations.
Normally, Chakra within the body does not exhibit an elemental affinity. It is only granted an attribute when using a corresponding ninjutsu or through deliberate manipulation. This is true even for Yin and Yang Release.
The Yang Release cultivation method recorded in his birth parents' notes was, in principle, the process of converting non-attribute Chakra into Yang-nature Chakra, which then strengthened the body during its circulation.
But Hiiro Rinko had realized something when he generated Cursed Energy using his spiritual power: If two different energies like Chakra and Cursed Energy could co-exist in his body, then perhaps Chakra of different attributes could co-exist as well.
For the five basic elements, the only benefit might be saving the time it takes to convert the Chakra nature, allowing for faster ninjutsu activation. But in the realm of Yin and Yang, it was a completely different story.
Yin Release: Chakra that uses spiritual energy as its source and has the property of "creating form from nothingness."
Yang Release: Chakra that uses physical energy as its source and has the property of "breathing life into form."
In terms of cultivation, although their natures were opposite, they also had common ground. If he could construct such 'cores' and get them running, it would be equivalent to constantly circulating both Yin and Yang Release cultivation methods at all times.
At first glance, this seemed like an outlandish, impossible idea. After all, no one in history had ever been able to imbue Chakra with multiple attributes simultaneously.
While "Combination Ninjutsu" existed, those were either performed by multiple people in coordination, or by a single person using extremely fast hand seals to cast multiple jutsu in rapid succession.
The closest thing to this concept would be the elemental Kekkei Genkai (Bloodline Limit).
For example, the Wood Release (Mokuton) used by the invincible Senju Hashirama was considered a mixture of Water and Earth natures. But this, in essence, was the creation of a brand-new Chakra nature, not the simultaneous application of two.
But Hiiro Rinko didn't believe it was impossible.
As a former Cursed User with experience in Black Flash and mastery of the 'Core of Cursed Energy,' his grasp of energy flow was already meticulous beyond words.
In fact, he had already succeeded in 'creating the cores.'
He set the 'brain,' the source of spiritual energy, as the core for Yin-nature Chakra. He set the 'heart,' the engine of physical energy, as the core for Yang-nature Chakra. He would mix non-attribute Chakra in his tanden (center), transmit it to the two cores, and then, by continuously infusing spiritual and physical energy, transform it into Yin and Yang Chakra. This part wasn't difficult for him.
He'd even reached a point where, once the cores had gathered enough, like oil droplets on soup clumping together, the non-attribute Chakra would automatically flow to the cores and be converted, without him needing to manually control it.
The problem now was how to operate these two different Chakra natures in parallel.
It wasn't that Rinko hadn't seen 'Yin-Yang Release' in the manga, but it was a late-game concept with no detailed principles. Here in this world, the records were just as scarce and vague, offering no reference value.
Compared to his other projects, this was the hurdle that had stumped Rinko for the longest time, and he foresaw that he might not make any progress for years to come.
But that's just what research is, isn't it? Most great discoveries are born from improvisation and intuition.
Rinko felt he was just missing that one, single spark of inspiration.
"Speaking of which, I hear that Rasa guy is graduating early."
Thinking of Kekkei Genkai, Rinko thought of his red-haired classmate with the perpetually sour face.
That guy had recently been discovered to have a talent for Lightning-nature Chakra and, as a result, had been taken in as a disciple by the Third Kazekage.
Kekkei Genkai can be broadly divided into two categories. The first is the elemental-type, which creates a new Chakra nature by mixing different ones. The other is the 'physical mutation' type, which manifests directly in the body's organs.
Most elemental Kekkei Genkai are new natures developed by a single, extraordinarily talented shinobi. Because the ratios of the two natures can differ, even the same combination might not produce the same new nature, and even the same Kekkei Genkai can have different manifestations.
But what is certain is that once a new Chakra nature is mixed, this Kekkei Genkai is recorded in the shinobi's genes and passed down to the next generation via blood.
The Third Kazekage's Magnet Release seemed to be an ability he was born with, but if judged by its attributes, it was a mixture of Wind and Lightning.
The still-single Third Kazekage clearly intended to pass on his Kekkei Genkai by teaching the next generation how to fuse the Magnet Release nature. Of course, it was also possible he was just using 'teaching a student' as an excuse to escape his paperwork.
But regardless, this real-world situation was enough to prove that the widely-circulated belief that "a Kekkei Genkai can only be inherited by blood" was pure nonsense.
Because of this, you'd occasionally hear voices in the Shinobi World claiming that elemental Kekkei Genkai aren't true Kekkei Genkai. This idea was probably spread by the 'physical mutation' families.
But that just made it even funnier. Setting aside things like the Shikotsumyaku (Dead Bone Pulse), every Dōjutsu (Eye Technique) Kekkei Genkai in this world was practically 'hot-swappable.' Anyone could pluck one out, slap it in, and use it on the spot. They were more convenient than a USB drive.
Rinko knew this was just a visual representation, and that in reality, you had to consider compatibility and other factors, with various side effects if you weren't a match.
But anyone who had read the later parts of the manga could never forget those scenes. The stereotype was set in stone.
But who cares if it's a Kekkei Genkai or not? If you can learn it, or pluck it out and use it, isn't that better? Such convenient, useful things should be utilized to their fullest extent.
Rinko's own Wind and Water Chakra... in Kirigakure, the Land of Water, Ice Release (Hyōton) was a famous Kekkei Genkai made from that exact combination. He'd occasionally tried mixing them, just to see if he could create Ice Release to pass the time.
"Ah... actually, I just got the notice, too. They want me to graduate early."
Rinko's casual comment, however, made Pakura look away guiltily.
"Misawa-sensei said… a Jōnin is willing to be my mentor..."