"Is it all gone..."
Shinji murmured softly in the laboratory.
This was a drawback of Sage Arts, or rather, a flaw: the natural energy in a given area is finite.
In lower-level confrontations, ninjas who mastered Sage Arts were limited only by the speed at which they could absorb natural energy; they didn't need to worry about whether there was enough natural energy in the surrounding environment.
But once one's strength reached a certain level, the abundance or scarcity of natural energy in the environment became a crucial factor affecting the upper limit of a Sage Mode user's power.
In the original timeline, during Naruto and Sasuke's final battle at the Valley of the End, Naruto briefly drained all the natural energy in the terrestrial environment at that time.
In other words, in a clash of strength approaching the Quasi-Six Paths level, the possibility of briefly draining the environmental natural energy already existed. If the level of confrontation went even higher, the insufficiency of natural energy would inevitably become even more pronounced!
Gathering his thoughts, Shinji began to single-mindedly tame the massive amount of natural energy he had inhaled into his body.
With his previous attempts, he had gained quite a bit of insight into taming natural energy. Moreover, relative to his terrifying 'Six Paths Level' chakra volume, the natural energy he just inhaled actually occupied a very limited proportion. So, while it seemed difficult to tame, it wasn't actually that hard.
Soon, this inhaled natural energy was completely tamed by Shinji.
Next came the methodical process of fusing natural energy into chakra at a specific ratio to refine 'Senjutsu Chakra' containing natural energy.
In this step, Shinji did not copy Haku's ratio.
Because Haku's own chakra volume was limited, to refine more Senjutsu Chakra, he had to fuse natural energy at the limit of his body's ratio.
For the 'Six Paths Level' Shinji, however, this was unnecessary.
On the contrary, what Shinji needed to do was minimize the proportion of natural energy infused, because of the constraint of the environmental natural energy cap.
"Sage Mode, activate!"
As Shinji opened his eyes, he entered a Sage Mode unique to himself.
Perhaps because his 'Six Paths Level' chakra intensity was too high, or because the proportion of natural energy in his refined Senjutsu Chakra was small, the changes in his physical appearance after activating 'Sage Mode' were extremely subtle—so subtle that even he found them hard to distinguish.
"Heh..."
Shinji smiled faintly.
This kind of chakra mode with no physical changes could sometimes play an unexpected role, such as in sneak attacks!
Then, Shinji began to sense the changes in his body.
The most obvious was the improvement in sensory perception. Under 'Sage Mode', his already formidable sensory abilities were further enhanced.
Subsequently, he tested it out; his speed and strength also saw significant improvements.
However, since his own body had already been developed to the limit, the improvement from 'Sage Mode' appeared relatively limited. But there was one point that satisfied him greatly: under 'Sage Mode', his body's durability increased considerably.
Regarding the effects of 'Sage Mode', Shinji was neither pleasantly surprised nor disappointed.
At his level, for 'Sage Arts' to bring such a noticeable improvement was already quite good.
To charge further up towards 'Kekkei Mōra', it wasn't something 'Sage Arts', or any other secret technique or chakra mode could achieve. That required the God Tree to absorb the energy of a planet and swallow a real Otsutsuki to condense a 'Chakra Fruit'!
Having mastered 'Sage Mode', Shinji began to consider how to integrate natural energy into the 'Karma' he developed.
Because 'Karma' contained his will, as long as he could successfully inject natural energy into 'Karma' and transform the chakra inside 'Karma' into 'Senjutsu Chakra', then the person activating 'Karma' could utilize the 'Senjutsu Chakra' within it, even if they hadn't mastered Sage Arts themselves.
'Senjutsu Chakra' offered limited improvement to Shinji because Shinji was already strong enough.
But for people like Karin, Hikari, and Sasuke who had not yet mastered 'Sage Arts', once they could use Senjutsu Chakra, the improvement in their strength would be very obvious. Perhaps adding natural energy to 'Karma' would become the final weight determining whether they could break through the threshold of 'Six Paths Level' after activating 'Karma'!
The experiment was completed very quickly. Shinji exerted almost no effort to edit natural energy into 'Karma', changing the attribute of all chakra within 'Karma' to 'Senjutsu Chakra' containing natural energy.
"Phew..."
Shinji exhaled lightly after completing the editing.
The reason it was so easy was thanks to his terrifying control over his own chakra, and in this regard, the 'Twelve Houses' (Zodiac) technique he developed contributed significantly.
This extreme control over every organ and every muscle in the body subtly improved his control over his body and high-precision control over chakra.
Although as his strength continued to rise, the amplification effect of the 'Twelve Houses' on taijutsu gradually weakened—after all, even Kaguya Otsutsuki, who was least skilled in taijutsu, could easily achieve the power level of 'Night Guy' with every strike once her level reached a certain state.
But the improvements in all aspects brought by the ascetic cultivation of the 'Twelve Houses' were still engraved in Shinji's body and his instincts.
Soon, Shinji began live experimentation again.
This time, because he changed the properties of the chakra in 'Karma' to Senjutsu Chakra, Shinji appropriately lowered the amount of chakra in 'Karma' so that the recipient could withstand the energy of 'Karma' more easily.
The White Zetsu experimental subject followed Shinji's instructions and activated 'Karma'. Its aura climbed rapidly, reaching the Super Kage level in just a few breaths.
"It seems that even with the addition of natural energy, it can't make an ordinary White Zetsu clone step into the 'Six Paths Level'..."
Shinji remained expressionless and continued to observe.
As time passed, the White Zetsu clone with active 'Karma' safely passed the five-minute mark, then ten minutes, then fifteen minutes!
A look of joy gradually appeared on Shinji's face.
When it reached sixteen minutes, the White Zetsu clone exited the 'Karma' state. This wasn't because Shinji's 'Karma' was unstable, but because it had reached the limit time for a single activation.
Because 'Karma' itself was a technology developed by the Otsutsuki clan for reincarnation, the process of activating 'Karma' would cause the activator's body to be influenced by the will contained in 'Karma', or even possessed. Therefore, sixteen minutes was the safety time set by Shinji. As long as it was controlled within this time, one would not be too deeply affected by 'Karma'.