"Sage Art?"
Itachi repeated the somewhat unfamiliar term to himself. Natural energy, what Kagetsu had mentioned—it was a bit difficult for his young mind to fully understand.
"You just need to know that it's a technique above Ninjutsu." Kagetsu didn't explain in detail right away. Instead, he simply gave Itachi a rough idea.
This technique was an experiment!
An attempt to absorb natural energy into the body and mix it with chakra—but shifting this step of Sage Mode from inside the body to outside of it.
In the end, his attempt was both a success and a failure.
Success because he achieved the original goal of the technique—moving the process of blending natural energy with chakra outside of the body, meaning the fusion happened after the Ninjutsu was released.
Failure because its power was far from the destructive force of true Sage Arts.
While it was stronger than Fire Release techniques of the same level, the difference in strength wasn't large enough to be overwhelming.
In other words, this technique didn't provide the same absolute dominance that Sage Arts had over regular Ninjutsu.
However, its difficulty in training was significantly higher than an ordinary Fire Release technique of the same level.
Even though Kagetsu had simplified and stabilized the process as much as possible, it had only gone from being something only exceptionally gifted people could learn to something still extremely difficult to master.
Realizing that this path was like Orochimaru's abandoned and modified Cursed Seal experiments—unable to keep up—Kagetsu ultimately changed his approach.
Instead of obsessing over creating these incomplete techniques, he shifted his focus to researching and developing ways to perceive and interact with natural energy.
Itachi nodded silently at Kagetsu's response, not pressing further. Though he was still young, children in the ninja world matured early.
As the clan leader's son, he had also been taught many rules beyond just Ninjutsu.
The elders had been constantly reminding him before every outing lately, repeatedly emphasizing that he must present himself as steady and exceptional in front of Kagetsu.
So, even though he was curious about natural energy and Senjutsu, when he noticed that Kagetsu didn't want to explain, he suppressed his questions.
"If you master this technique proficiently, I will teach you its advanced form. At that point, this technique will be yours alone," Kagetsu said, patting Itachi, who seemed very understanding.
"What counts as mastery?" Itachi wanted a definite answer. This technique suited him well.
Unlike other Fire Release techniques, which required gathering chakra in the mouth before releasing it, this one could be used through the hands or even the feet.
Of course, like other Fire Release jutsu, it could also be unleashed through the mouth.
However, Itachi wasn't capable of that yet, so he followed the standard approach by using his hands.
If it were the Hyuga clan, who could release chakra from all over their bodies, they might be able to use this jutsu from various body parts.
Itachi wasn't sure if Kagetsu's definition of mastery referred to being able to release the technique through hands, feet, and mouth or to a deeper understanding and control of the technique itself.
Or was it both?
"Since you can already sense the flowing natural energy, let's say mastery is when you can freely integrate it into this jutsu in the correct proportions."
Seeing the slightly surprised expression on Itachi's face, Kagetsu smiled and added, "Of course, if you have any questions, you can always ask me or Shisui. I will also share my research notes and experience with you."
Itachi nodded again upon hearing this.
This style of teaching—where he was given freedom while also receiving comprehensive guidance—felt familiar to him. His father had once taught him the same way.
He would demonstrate a technique in its entirety, answer any questions, highlight key points, and then leave the rest to Itachi's own understanding and effort.
From refining chakra to mastering his first Fire Release jutsu, the Great Fireball Technique, Itachi took less than seven days. He could already perform it properly, with a certain level of destructive power.
Itachi saw Kagetsu's actions as a kind of test from his teacher, which subconsciously made him feel a sense of urgency.
Aside from being nurtured and guided, he naturally had a calm and composed personality. He didn't particularly care about learning an extra jutsu, but if that jutsu was tied to an assessment or someone's expectations, he would push himself to meet those expectations as soon as possible.
In other words, even though he was more mature than children his age, he was still at an age where he sought recognition.
"Don't rush. This is a test, but not the kind you think it is." Kagetsu immediately saw through Itachi's thoughts.
He patted the boy's head and explained when he noticed his confused expression, "This jutsu has something special about it. With your sensitivity, you must have noticed by now, right?"
"Is it natural energy?" Itachi thought for a moment before answering.
"Yes, natural energy! This jutsu allows you to perceive and come into contact with natural energy." Kagetsu paused before continuing, "To be honest, I didn't expect you to master this jutsu so quickly and even successfully perform it."
"This jutsu… was it specifically created to help someone master natural energy?" Itachi instinctively recalled what he had experienced while learning it.
Unlike the other Fire Release jutsu he had learned, this one was much harder to control. If natural energy wasn't properly integrated, it could easily explode at close range, harming the user instead.
The reason he had managed to learn it so smoothly and quickly was thanks to Shisui's guidance and protection.
Now, from Kagetsu's tone, Itachi keenly sensed that his teacher wasn't concerned about the power or difficulty of the jutsu itself. Instead, he was particularly focused on whether Itachi could sense and master natural energy.
"You really are talented, Itachi!"
Kagetsu finally understood why teachers always favored and appreciated smart students.
A disciple who could grasp things instantly, understand them with just a word, and quickly comprehend the key points—not only gave a great sense of accomplishment but also saved a lot of effort and time.
For Kagetsu, the latter was especially important.
No matter how Itachi's personality and style would develop in the future, at this moment, he had certainly gained more recognition in Kagetsu's eyes.