Chapter 48 – Conceptualizing a Knockoff Yin Seal
The reason Ryuya wanted to develop a chakra sealing technique similar to the Yin Seal was simple: to dramatically increase his combat power in a short period of time.
In the shinobi world, pure taijutsu specialists like Might Guy and Rock Lee were, after all, rare exceptions. The primary standard by which a ninja's strength was judged was still the amount of chakra they possessed.
The quantity of chakra within a ninja not only determined the power of the ninjutsu they could unleash, but also directly affected their combat endurance.
It was a decisive factor in determining victory or defeat.
In battle, chakra monsters such as jinchūriki or Kisame Hoshigaki could recklessly unleash large-scale ninjutsu. Whether in one-on-one combat or on the battlefield, they could exert overwhelming destructive power.
On the other hand, someone like Kakashi, who possessed an ordinary physique and was further burdened by the Sharingan, often had no choice but to rely on strategy and precise chakra control to fight.
After a hard-fought battle, even if he wasn't injured, he would still be exhausted for several days.
Because the amount of chakra a ninja could possess was inherently limited—and because chakra, as a form of energy, was extremely difficult to store—only a very small number of ninja in the shinobi world could boast "ton-level chakra reserves."
They were basically walking cheats.
In Ryuya's understanding, the only technique in the entire shinobi world capable of solving the problem of chakra storage was the Yin Seal.
This was an S-rank auxiliary fūinjutsu that allowed a ninja to accumulate massive amounts of chakra over a long period of time. Once the seal was released at a critical moment in battle, it could instantly provide an enormous surge of chakra.
It was precisely because she possessed the Yin Seal that Tsunade could use Creation Rebirth and the Strength of a Hundred Technique.
For Ryuya—who already possessed the Glutony Seal and the Body Activation Secret Technique—the speed at which he could refine chakra was no longer the key factor limiting his rapid growth in strength.
The true bottleneck was the upper limit of chakra that his still-young body could contain.
Although this limit would continue to increase as Ryuya's body matured and as the Body Activation Secret Technique improved his physique, such growth required a long period of time.
It couldn't allow him to reach a significant level of power in the short term.
A chakra sealing technique like the Yin Seal, however, was the perfect solution.
With the powerful functionality of the Glutony Seal as support, Ryuya could fully unleash his strength in battle and then rapidly recharge, maintaining high combat power for extended periods of time.
Moreover, there was an even more important reason.
Ryuya wanted to learn Senjutsu.
Senjutsu was a stepping stone that could allow him to leap directly into the top tier of the shinobi world.
After obtaining the Ryūchi Cave Senjutsu scroll from Orochimaru, Ryuya immediately began studying it with great urgency.
After deciphering the training methods of Ryūchi Cave Senjutsu, Ryuya discovered that there were three key conditions for using Senjutsu.
The reason why so few ninja in the shinobi world could use Senjutsu was mainly because the requirements were extremely harsh.
The first condition—and the one that blocked roughly 99% of all ninja—was the perception of natural energy.
Without the aid of the sages from the Three Great Sage Regions, it was exceedingly difficult for humans to independently sense and absorb natural energy.
At present, only Jūgo in the entire shinobi world was capable of doing so on his own.
Jiraiya and Naruto, on the other hand, both mastered Senjutsu with the assistance of Fukasaku.
The second key factor affecting Senjutsu training was a ninja's chakra control.
Ordinary ninjutsu relied on activating the chakra within one's body—chakra formed from the fusion of physical energy and spiritual energy.
Senjutsu chakra, however, was created by absorbing natural energy and perfectly integrating it with those two energies.
To activate it, all three energies had to remain in perfect balance—one-third each.
If natural energy exceeded one-third, the user would be swallowed by it and begin to turn to stone.
If it fell short of one-third, Sage Mode could not be activated at all.
The third key factor was the amount of chakra within a ninja's body.
From a purely technical standpoint, it seemed that mastering the first two conditions was enough to learn and use Senjutsu.
However, in actual combat, chakra quantity was also a decisive factor.
This was because the vast majority of Senjutsu techniques were extremely powerful and consumed large amounts of Senjutsu chakra. To maintain Sage Mode, a ninja needed to keep a massive reserve of chakra to ensure the balance of the three energies.
Otherwise, even a small misstep could result in being eroded by natural energy.
This was clearly demonstrated by the Fourth Hokage, Minato Namikaze.
As Jiraiya's disciple, Minato had indeed mastered Senjutsu, yet before his death, he rarely used it on the battlefield.
Even with the godlike technique Flying Thunder God, Senjutsu would have provided Minato with a terrifying boost in combat power.
The reason he refrained from using it was simple—his chakra reserves were insufficient. Using Senjutsu would have drastically reduced his combat endurance.
By the time of the Fourth Great Ninja War, however, after gaining Nine-Tails Chakra Mode within the Shinigami's stomach, Minato was able to enter Sage Mode almost instantly on the battlefield.
At present, Ryuya met none of the three conditions required to learn Senjutsu.
As for chakra control, he could continuously grind experience using Shadow Clones.
But when it came to sensing natural energy and increasing his chakra reserves, he had no viable solution for the time being.
For now, Ryuya decided to prioritize solving the issue of chakra quantity.
With enough chakra, even if he still couldn't practice Senjutsu, his overall strength would increase dramatically.
Using his biological chip, Ryuya made an estimate. At his current rate of growth, if he followed the conventional path, it would take him three to four years to meet the requirements to learn and use Senjutsu.
That was precisely why he was so eager to develop a knockoff version of the Yin Seal.
The fastest way to create a knockoff Yin Seal would naturally be to copy the original—but that was impossible for Ryuya.
As an S-rank auxiliary fūinjutsu, the Yin Seal had only ever been used by Uzumaki Mito, Tsunade, and Sakura Haruno throughout the entire Naruto timeline. It was a secret technique passed down strictly through a master-disciple lineage.
At present, only Tsunade knew the actual training method. Konoha's secret archives likely didn't even possess a cultivation scroll.
Otherwise, given the personalities of Danzō and Orochimaru, there was no way they would have ignored such a powerful technique.
Even if a Yin Seal scroll did exist in Konoha's secret vaults, given Ryuya's current status and contributions to the village, obtaining it would be virtually impossible.
However, after a long period of contemplation, Ryuya had already formed a preliminary idea.
He would start his research from Summoning Jutsu and Contract Seals.
The essence of chakra was the fusion of physical energy and spiritual energy. To store chakra, one had to be able to store both of these components.
As for physical energy, the Akimichi clan's secret techniques already contained ingenious methods for doing so. Overcoming this aspect would not be difficult for Ryuya.
In terms of spiritual energy, Ryuya had previously discovered runes within summoning contracts that functioned similarly to storing spiritual will.
Moreover, contract seals could completely sever the contractual link between a ninja and their summoned beast. This alone proved that they contained runes capable of preventing spiritual will from permeating or dispersing.
If he could replicate the runes related to spiritual will from summoning contracts and contract seals, it might very well be possible to create an entirely new sealing technique.
Once the problem of storing spiritual energy was solved, storing chakra would no longer be difficult.