The core structure of the Rasengan is an irregularly and rapidly spinning clump of Chakra, which can only maintain stability for a few seconds without external control.
To turn the Rasengan into a long-range attack, he either had to add Chakra nature transformation for structural reorganization, or directly use the Chakra shroud as an extension cord to connect to it.
The latter was the exact principle behind the Chakra Arms holding the Rasengan in Kurama Chakra Mode.
Speaking of which, when he watched Boruto in his past life, Boruto's Rasengan could be thrown without adding nature transformation, and it would even turn invisible.
It seemed to have something to do with Boruto unintentionally adding a trace of Lightning Chakra when practicing the Rasengan, but right now, his Chakra nature was only Wind.
Mastering nature transformation was another crucial foundation, preparing him for the future Wind Release: Rasenshuriken and laying a solid groundwork for learning other composite ninjutsu.
Once the Chunin Exams were over, he would find an opportunity to ask Kakashi about the specific training methods for Chakra nature transformation, especially how to get started with attributes other than Wind Release.
In this regard, Kakashi was Konoha's recognized expert. As a Sharingan wielder who had copied over a thousand types of ninjutsu, his understanding of the five attributes and his switching techniques were, in some aspects, even more comprehensive than Hiruzen's.
With this in mind, Naruto raised his right hand again, holding the Rasengan in close combat style to continue clearing the remaining rocks.
One massive boulder after another turned into dust under the shaving of the Rasengan.
Naruto knew better than anyone just how sensitive the Ninja World could be to details. In his past life, he had failed because of details. In this life, he would not make the same mistake again.
After the last remnant of rock was ground into powder by the Rasengan and dispersed into the pool, Naruto prepared to deactivate the Kurama Chakra Mode he had been training in all night.
"Hahaha... I sensed space fluctuations!"
An excited shout came from the direction of the cavern.
A clone raised his fists in the air, startling the other clones nearby.
Immediately afterward, several more clones jumped up from the ground.
"I can carve Chakra onto the formula!"
"I can sense the Chakra I carved! The approximate direction and distance of the location, I can sense it all!"
Naruto's eyes lit up and he formed a release sign with his hands.
Bang, bang, bang, bang...
In an instant, forty Kurama Chakra Mode clones turned into smoke at the exact same moment.
Immediately after, over forty sets of training memories flooded into Naruto's mind: the Flying Thunder God formula diagram, the positioning and calculation of spatial coordinates, the tactile sensation of Chakra engraving, and the initial perception of spatial fluctuations.
Each memory brought insights and details from different angles, converging and colliding at the same moment.
Naruto stood in place with his eyes closed, activating Absolute Control. In his mind, this information was categorized and synthesized.
Under the integration of Absolute Control, these scattered breakthroughs quickly assembled into a complete logical network.
The two most critical steps—the inscription of the Chakra formula and the spatial sensing of the inscribed formula—transformed from mere principles into tangible intuition in Naruto's cognition.
Naruto opened his eyes and took a Kunai out of his ninja tool pouch. He held the Kunai in his right palm, gathered Chakra at his fingertips and prepared to carve.
The Flying Thunder God Technique inscription does not have a fixed pattern. Every user creates a unique mark based on their own Chakra characteristics.
Tobirama's Flying Thunder God Mark was a complex rune, while Minato's mark consisted of the characters for "Sword of Endurance and Love." It was a memento of a certain promise between him and Kushina, and it also symbolized the will to protect Konoha.
Naruto didn't intend to be the same as them. He thought for a moment, and a pattern flashed through his mind.
A circle with the Uzumaki clan symbol inside it.
This pattern was an anchor to his past life on Earth, constantly reminding him of where he came from. It also symbolized his current identity as an Uzumaki.
The Chakra at his fingertip landed the first stroke on the metal surface of the Kunai handle.
Naruto's movements were slow because inscribing the Flying Thunder God formula required extremely precise control over the density and penetration depth of the Chakra.
If the Chakra was too shallow, the inscription would not last. If the Chakra was too deep, the metal itself would be unable to withstand it and would shatter.
Absolute Control allowed Naruto to perceive the force at his fingertips with extreme precision, keeping the depth of every stroke at the optimal point of the metal material's tolerance.
When the final stroke was finished, Naruto moved his finger away from the Kunai.
He gripped the Kunai with the Flying Thunder God Mark carved into it, weighed it to confirm the feel, and then tossed it forward.
The Kunai embedded itself into a rock crevice about fifty meters away on the opposite side of the waterfall pool.
Naruto closed his eyes, focusing his attention on the specific sensory frequency of the Flying Thunder God Technique.
The next moment, he clearly sensed the existence of the mark on the Kunai. In his perception, the distance, direction, and even the state of the mark itself were perfectly clear.
Naruto activated his Chakra according to the activation sequence of the Flying Thunder God Technique.
Unlike ordinary Body Flicker Techniques that require hand seals, the activation of the Flying Thunder God Technique relies entirely on the spatial channel connection between the formula and the user.
The moment the Chakra activates the formula, the expanding spatial channel pulls the user point-to-point along the coordinates.