After acquiring the [Senjutsu Body], Naruto had no need to learn Mount Myōboku's version of Sage Mode.
His body could absorb natural energy on its own and combine it with his chakra to produce senjutsu chakra.
In a sense, Naruto possessed a unique Sage Mode that remained permanently active. Senjutsu chakra constantly circulated through his body, so he wasn't restricted by Mount Myōboku's five-minute time limit. Nor did he grow horns like practitioners of Ryūchi Cave's Sage Mode.
However, he still needed to learn techniques such as Frog Kata and Frog Strike.
Those were applications of natural energy rather than abilities exclusive to Mount Myōboku's Sage Mode.
It was no different from the Leaf's taijutsu styles. Any shinobi could learn them with the proper instruction, regardless of which village they came from.
"I guess I can call myself a sage now too," Naruto thought smugly.
Ten days passed.
Naruto finally mastered Frog Kata and Frog Strike. He also succeeded in using senjutsu chakra to perform Wind Release ninjutsu.
The results were disastrous.
Most of Mount Myōboku's vegetation was ripped from the ground. Trees and enormous plants flew through the air as sand and stones swept across the mountain. Even the sleeping Great Toad Sage was startled awake.
Had Fukasaku not stopped Naruto in time, the boy might have devastated the whole of Mount Myōboku.
Afterward, several of the elder toads gathered for a serious discussion.
Their conclusion was unanimous.
"You should leave," Fukasaku told Naruto. "We truly have nothing left to teach you—and frankly, we're afraid to let you stay any longer."
Naruto had also hoped to learn the sound-based genjutsu used by Fukasaku and Shima, [Demonic Illusion: Toad Confrontation Chant].
Unfortunately, he was mercilessly informed that the technique could only be mastered by actual toads with the proper vocal organs.
"Damn. That's cold."
Once the disappointment faded, Naruto began considering his present condition.
Although his body now contained senjutsu chakra, his total reserves were still insufficient.
Losing his two Sage Bodies had caused his chakra capacity to plummet. After experiencing those enormous reserves, returning to his original capacity left Naruto feeling strangely empty.
He desperately wanted to regain chakra reserves comparable to those of a tailed beast, then convert that chakra into senjutsu chakra with natural energy.
If he possessed tailed-beast-level reserves, he could become a true [Mage Emperor]—a walking [Nuclear Fortress] capable of flattening battlefields with ninjutsu.
Just imagining it was exhilarating.
Naruto considered the problem carefully and came up with two possible methods.
The first was to borrow the Nine-Tails' chakra and attain the same Nine-Tails Chakra Mode used by the original Naruto.
However, borrowed chakra was ultimately still borrowed. It didn't truly belong to him, and Naruto wasn't certain whether the Nine-Tails' chakra could combine properly with natural energy.
The second method was to take Samehada from Kisame.
Like Kisame, Naruto could use the sword to devour other people's chakra and convert it into his own. His [Senjutsu Body] could then combine that stolen chakra with natural energy.
There was also the ancient kingdom of Rōran.
The Dragon Vein beneath Rōran contained an enormous amount of chakra. Samehada should be capable of devouring that as well!
The more Naruto thought about it, the more excited he became. He wanted to find Kisame immediately.
Without another moment's hesitation, he left Mount Myōboku.
Thus, after spending only ten days there, Naruto was driven away—leaving a ruined landscape behind him.
Poof!
White smoke dispersed around Naruto.
"Come on, sir! Come and play with us!"
Naruto had returned from Mount Myōboku directly beside Jiraiya.
Seeing how comfortably Jiraiya had settled into the establishment—and hearing the flirtatious laughter surrounding him—Naruto's face darkened.
That old pervert had clearly spent the entire ten days indulging himself.
"Fine. Let's make this even more exciting for you."
A malicious grin spread across Naruto's face.
He condensed a whirlwind in his palm and casually tossed it upward.
Whoosh!
The entire roof was torn away.
Sunlight flooded the dim room for what was probably the first time since the building had been constructed.
The women shrieked and hurriedly covered themselves, while Jiraiya pulled up his trousers and fled from the building.
Naruto chased after him with a wicked grin.
"Hey, Naruto!" Jiraiya snapped. "Why are you back already? Did you give up on Sage Mode and come here just to cause trouble for me?"
"I'm back because I already mastered it."
Naruto raised one hand.
Senjutsu chakra gathered above his palm, forming an enormous sphere.
[Sage Art: Big Ball Rasengan]
Jiraiya froze.
"You little… What kind of monster are you?!"
He stared at the giant Rasengan and felt the terrifying energy contained within it. The corners of his mouth twitched uncontrollably.
"Is Mount Myōboku's Sage Mode really that easy to master? Even I haven't perfected it yet!"
Jiraiya suddenly noticed something else.
His eyes widened as he pointed at Naruto.
"Wait! Where's your pigmentation? You don't have any of the markings associated with Sage Mode! But that Rasengan clearly contains an enormous amount of natural energy!"
"Heh."
Naruto smiled proudly.
"That's because I'm a genius. My body can absorb natural energy automatically."
"What?"
Jiraiya found that almost impossible to believe.
After hesitating for a moment, he moved aside, bit his thumb, and summoned Fukasaku. The man and the old toad began whispering to each other at a distance.
Naruto didn't remain idle.
He closed his eyes and sensed the natural energy around him.
As expected, its concentration in the outside world couldn't compare with that of Mount Myōboku. Once Naruto exhausted his senjutsu chakra, replenishing it here would take considerably longer.
"Wait. What about the star meteorite I took before? How did I forget about that?"
Naruto slapped his forehead.
He quickly retrieved a storage scroll and released the sealed meteorite from Hidden Star Village.
The moment he held it, he sensed the strange radiation emanating from the stone.
That radiation stimulated his body and dramatically accelerated the rate at which he absorbed natural energy.
Any physical damage caused by the meteorite's radiation was immediately repaired by the senjutsu chakra circulating through Naruto's body.
"This thing really is a treasure!"
Delighted, Naruto tucked the meteorite inside his clothes.
With it, he no longer had to worry as much about replenishing natural energy while fighting in the outside world.
After some time, Jiraiya returned with a complicated expression. His eyes contained both delight and helplessness.
Having such an abnormally powerful student placed an enormous amount of pressure on him as the teacher.
"Naruto, with your current strength, you may already be close to my level."
Jiraiya spoke with obvious reluctance before abruptly changing his tone.
"Of course, you still lack enough real combat experience. From now on, I'll find some wandering shinobi for you to fight so you can build that experience."
"Sounds good!"
Naruto immediately became excited.
He had already planned to kill more shinobi and accumulate system points. Jiraiya had simply brought up the idea first.
However, killing wandering shinobi wasn't Naruto's only objective.
He also wanted to seize Samehada from Kisame.
Naruto's eyes flickered as he looked at Jiraiya.
"Why don't we go after Akatsuki's members directly? They're all powerful. Fighting them should give me far more experience."
"Well…"
Jiraiya hesitated.
The entire reason he had taken Naruto away for training was to increase the boy's strength before Akatsuki began hunting the jinchūriki and the Nine-Tails in three years.
He had never expected Naruto to suggest hunting Akatsuki first.
Then again, Naruto's current strength had already exceeded all of Jiraiya's expectations. He had reached Jiraiya's original goal almost immediately.
Noticing his hesitation, Naruto continued persuading him.
"Akatsuki is extremely powerful, and it must have several formidable members. Instead of waiting for them to come after us in three years, why don't we weaken them now?"
Jiraiya still couldn't bring himself to agree.
He shook his head.
"Akatsuki's strength is beyond your imagination. Every member possesses power comparable to a Kage from one of the Five Great Shinobi Villages."
As he spoke, Jiraiya remembered Uchiha Itachi.
He recalled the unnatural black flames Itachi had used at the hotel, and a trace of fear passed through his eyes.
"If we alert them now, they may begin their attack ahead of schedule. We should take the safer approach and build up your combat experience first."
Naruto could only feel helpless.
He understood Akatsuki far better than Jiraiya did.
He even had his female avatar planted inside the organization as a spy.
Even if he killed Kisame and provoked Akatsuki, Naruto wasn't particularly afraid. With the Flying Thunder God Technique, he could always escape if the situation became dangerous.
Unfortunately, he couldn't explain any of that to Jiraiya.
Nor could he reveal the full extent of his abilities.
"Fine. I'll start by accumulating points through killing."
Naruto sighed inwardly.
"Once I have enough points, I'll obtain the [Fire God Form], [Lightning God Form], [Earth God Form], and [Water God Form]!"
That would be the first true step toward becoming a [Mage Emperor] and a walking [Nuclear Fortress].
He would also continue training the Eight Inner Gates and developing the Rasengan series.
Three years from now, when he appeared before the shinobi world again with all of that power…