Chapter 15: A Researcher Must Be Cautious
"Alright, alright, class is starting."
Having been told by Chiyo beforehand not to give Hiiro Rinko any special treatment, the Sensei simply called for quiet twice. Among these new students, the teacher still held some authority, and the noise quickly died down.
Seeing the classroom quiet, the unremarkable Suna shinobi began his lecture, reading straight from the book.
This class was 'Basic Shinobi Studies.' The first half of the textbook was just definitions for terms like shinobi, ninjutsu, and Chakra. Only in the middle did it get to content like Chakra refinement.
'The Shinobi Academy is so boring…'
Rinko listened for a while at first, felt the Sensei's lecture was even worse than Yūsa's notes, and immediately let his mind drift.
Of course, it was possible the Sensei was speaking in simple terms to accommodate the kids with no foundation, but what did that have to do with Rinko, who was already researching the optimal circulation of Chakra?
He only looked young; his mind hadn't regressed to that of a child. He just couldn't stand this kindergarten-level teaching style.
Rinko propped his cheek on one hand, and with the other, he took off the pendant from his chest, flipping it deftly between his fingers.
On the entire journey to Sunagakure, he had been studying this pendant, the last creation his parents had poured their all into.
The pendant's material was just ordinary jade, with nothing special about it. But as a container for Chakra, it left no trace, even to Chiyo's senses. When inactive, no one except Rinko could perceive the power within it.
This point alone was astonishing.
Whether it was the answers he'd pried from Chiyo on the road or the records in his parents' scrolls, all of it clearly stated that there was no such thing as an 'absolute' seal or barrier in this world.
No matter how meticulous a seal was, it could never be foolproof. In fact, due to the increase in complexity and layers, any tiny error could lead to a total collapse of the entire system.
The so-called art of barriers and seals (Kekkai and Fūinjutsu) never pursued complexity, but rather sought to achieve the greatest effect with the simplest means.
How to strike that balance was the essence of Fūinjutsu.
And yet, this pendant in Rinko's hand seemed to violate the most basic definitions of Sealing Jutsu in the Naruto world.
For him, however, he had seen many similar items, theories, and settings.
In his original world, there were Special Grade Cursed Objects that, in exchange for the cost of 'never harming humans,' gained physical durability that was nearly impossible to break. The source of this resistance was rooted in the basic concept of a 'Binding Vow.'
A Binding Vow (Shibari) refers to a pact or contract made with oneself or others.
By establishing a 'must do' or 'must not do,' one could gain something else in return. If the Vow was broken, one would suffer an 'unknown' punishment.
This was common knowledge in the Cursed World.
But even though it was common knowledge, almost no one knew why it worked that way, or why the punishment was 'unknown.'
Rinko had his own speculations. The Cursed Energy used by Cursed Users ultimately stemmed from the 'spirit' or 'psyche.' Since it was a power based on the mind, it was only natural that it would be affected by one's psychological state.
When making a Binding Vow, it was impossible not to be fully committed, to believe that 'this must be done.' Perhaps it was the power generated by that instantaneous resolve that formed the basis for the Vow's establishment.
Coincidentally, Rinko had seen a similar concept in the Hunter x Hunter manga.
In that manga, 'Nen,' the foundation of the entire power system, was the ability to freely manipulate the 'Aura' (life energy) flowing from the body. Everyone slowly emits a small amount of life energy, but most people cannot control its loss.
Controlling this energy required 'tempering and training the mind,' a cultivation process of strengthening one's own will.
Through this training, a Nen user would awaken various abilities based on their own nature.
Within Nen abilities, there were no 'absolutes,' but there could be things that were 'infinitely close.'
By placing a 'Vow' or 'Covenant' upon oneself during training, the more difficult the rule, the greater the power that could be unleashed.
Although Nen was built on life energy, what drove it was still the will, or the 'spirit'.
Considering he had truly crossed over into the Naruto world, Rinko felt he could still use Hunter x Hunter as a reference, even if he'd never personally experienced Nen.
And these 'Vows' or 'Bindings,' at their core, were the will of an individual having a tangible effect on reality.
'So, they must have unintentionally touched upon the power of a Binding Vow… No, not just that. Perhaps their dying will was also a factor…'
Rinko also remembered that in Hunter x Hunter, there was a concept called 'Post-Mortem Nen,' which was the idea that Nen left behind by a deceased user could never be consumed or absorbed.
To solidify one's entire life energy and lingering resentment into a near-permanent existence at the moment of death—this also showed that the 'spirit' could indeed strongly interfere with reality.
'In other words, I can try using Binding Vows to increase my strength here as well…'
Having sorted out these thoughts, Rinko planned to find an opportunity to try it.
Although he had already made one Binding Vow when he first awoke in this world—with the residual 'Vibration' in the body—that Vow's conditions and effects were both too vague to feel real.
And in that situation, he had neither the time nor the opportunity to test it repeatedly.
Since this was something he would be using on himself, he couldn't be too careful. Having miraculously received a second chance at life, Rinko was very precious about it.
"Um… Hiiro-kun? Why did you say that just now?"
More than halfway through the class, Karura—who had been sneaking glances at the daydreaming Rinko—finally gave in to her curiosity. She stealthily nudged his elbow and whispered like a conspirator.
"Hm? What?"
Rinko, whose acting was terrible and who relied entirely on his poker face, was, however, a natural-born talent at spacing out. His posture didn't change at all, and he didn't even turn his head as he responded to Karura.
"You know, when you said my Chakra flow was the smoothest…"
"Because it's a fact. In this whole class, besides me, your Chakra circulation has the fewest pauses and the least variation in speed."
"After that, the one with the most Chakra is that kid, and the easiest to sense is that girl."
Clipping the pendant back onto his chest, Rinko took out a pen, which was more suitable for pointing, and pretended to write a few words. He continued speaking, using the pen tip to point out two other children.
The first was a boy with short, reddish-brown hair. The second was a girl with dark green hair and brownish bangs.
Then, he added one more sentence.
"Aside from you three, there's no one else in this class worth paying attention to."
"Eh?"