He's still a man of action.
Seeing no one around, Naruto unzipped his pants and carefully performed a partial Multiplication Technique, enhanced by Yang Release Chakra, causing his… organ to rapidly expand.
It eventually reached a size completely unbefitting a twelve-year-old.
"It worked!"
"I never thought the Multiplication Technique could be used like this."
"This must be the correct way to use the Akimichi Clan's secret technique, right?"
Naruto looked down, eyes wide, unable to hide his delight.
He felt that from now on, when using the restroom at the Ninja Academy, he wouldn't need to stand a urinal apart from anyone else.
Which of the other male classmates wouldn't feel inferior?
Naruto stood by the stream, now a scorched, molten pit, raised his… thing, and thrust his hips forward.
"Whoosh!"
Urine shot out like an arrow.
A wave of relief washed over him; Naruto shivered slightly, pulled up his pants with both hands, and felt utterly satisfied.
"…"
Kurama watched, speechless for a moment.
"Kid, you… are so childish…"
"Skinny fox, what do you know? A man is a boy until he dies!"
Naruto retorted, and a wicked thought suddenly popped into his head.
What if Multiple Shadow Clone Jutsu was combined with the Multiplication Technique…
"No, I can't just randomly develop Ninjutsu; I'll become impure."
Naruto shook his head, casting the unhealthy thought aside.
"Since I've brought Chakra shape transformation to the [Master] level, I can now train in Rasengan."
Naruto's thoughts returned to the right track.
The reason he wanted to learn Rasengan wasn't because Rasengan was his signature Ninjutsu, but because Rasengan, as the only growth-type Ninjutsu that could be learned early on, was simply too important.
Rasengan requires no hand seals, can be performed with one hand, doesn't require specific Chakra flow paths, and is highly malleable, making it one of the very few growth-type Ninjutsu that can be "powered up with sheer force."
Generally speaking, Ninjutsu is like a spell, and flowing Chakra is like drawing a charm and casting a spell within the body.
Precisely because of this, Ninjutsu is limited by the Chakra flow path, and its power ceiling becomes fixed; it won't get stronger by simply injecting more Chakra.
No, to be precise, it's impossible to infuse more Chakra.
A Ninjutsu is equivalent to a type of firearm, a hose spouting water; the bullet caliber is fixed. If you want to increase its power (the Ninjutsu's Upper limit), the caliber cannot be changed, only the material of the bullet.
Which is Chakra!
For the same Ninjutsu, higher quality Chakra releases greater power.
Sage Chakra, Tailed Beast Chakra, and the Chakra of some special physiques and veteran powerhouses are definitely superior to ordinary Chakra.
Furthermore, once a Ninjutsu's power ceiling is fixed, the amount of Chakra consumed will also be relatively fixed.
When Naruto and Uchiha Sasuke perform the Fire Release: Great Fireball Jutsu, the amount of Chakra consumed is similar; it won't give Sasuke special treatment just because he's from the Uchiha Clan.
You can reduce the Ninjutsu's power by using less Chakra, but you cannot break its upper limit by increasing Chakra.
This is also why ordinary Ninja, besides refining their Chakra, must learn high-level Ninjutsu if they want to become stronger.
High-level Ninjutsu are not just difficult to learn; they are also more powerful, or their effects are more bizarre and unpredictable.
Otherwise, what's the point of something being difficult to learn?
I've mastered a difficult Ninjutsu, so I seem smarter?
If Ninjutsu could just be powered up by injecting more Chakra, then everyone would just learn C-rank Ninjutsu, right? Why bother learning harder Ninjutsu, just to show off?
Clearly impossible.
But!
There is one Ninjutsu that breaks the above conventions.
It requires no hand seals, and no fixed Chakra flow path.
It is the Ninjutsu—Light Ring Ice Pop Initiating Swirl Jiraiya Two-Style Ball—created by the Fourth Hokage Minato Namikaze, inspired by the Tailed Beast Ball fired by Four-Tails Son Goku and Five-Tails Kokuo, and developed with Jiraiya over three years for Kushina.
Abbreviated as… Rasengan!
Rasengan is a technique where Chakra is condensed in the hand, causing it to continuously flow in different directions and be compressed, forming a highly rotating, dense "Chakra sphere" with immense destructive power.
Of course, this immense destructive power is relative.
When using the same amount of Chakra, Rasengan's power is far less than other A-rank Ninjutsu.
Otherwise, all A-rank Ninjutsu would become clowns.
Rasengan has only two advantages.
One is that it can be "powered up with sheer force," breaking the fixed power of Ninjutsu and allowing it to be strengthened by injecting more Chakra.
The other is its incredible malleability.
Injecting more Chakra turns Rasengan into Great Ball Rasengan and Super Great Ball Rasengan.
By fusing Chakra nature transformation, it can become Wind Release: Rasengan, Water Release: Rasengan, Fire Release: Rasengan, and so on.
What kind of tricks can be performed depends on the creator's imagination and ability.
"My Chakra nature transformation and shape transformation are both [Master] level now, plus my own vast and abundant Chakra, Rasengan is practically a Ninjutsu tailor-made for me, how could I not learn it?"
Naruto chewed on a slender blade of grass, found a clean patch of grass to lie down on, leaning against the base of a tree, letting the dappled light filtered by the branches and leaves fall upon him.
He was thinking about how to train for Rasengan.
Now there was no Jiraiya to teach him hands-on.
He could only figure it out himself.
Fortunately, the most difficult hurdle in training for Rasengan—Chakra shape transformation—had already been overcome by Naruto.
"The principle of Rasengan is simple and crude; I remember Jiraiya's teaching method involved a water-filled balloon, right?"
Naruto sifted through his "past life" memories.
Jiraiya's Rasengan training method was divided into four steps:
Phase one: Gather Chakra in the palm of your hand.
Phase two: Place a water-filled balloon on your hand, then release Chakra to make the water inside the balloon move erratically until the balloon bursts.
Phase three: Replace the water balloon with a rubber ball and pop the rubber ball.
Phase four: Combine all the previous elements, gather high-density Chakra in your hand, continuously release it, maintain it, and finally solidify it into a small typhoon.
"Doesn't seem too troublesome."
"Let's try the first step first."
Naruto spat out the bitter grass blade from his mouth, raised one hand, curled his five fingers into a claw, then activated the Chakra within his body, continuously releasing and gathering it in his palm.
Soon.
A bright blue orb of light appeared.
Step one, complete!
Next was phase two.
"I don't have a water-filled balloon, but the essence is just to make the Chakra move irregularly, right? The water balloon just serves as an aid."
Naruto's thought moved, and he controlled the Chakra within the bright blue orb in his hand to move in different patterns.
This step was very difficult.
But for Naruto, it was as simple as could be.
Controlling Chakra was like moving his own limbs!
"What is this little brat up to now?"
Kurama, sprawled in his sealed cage, couldn't help but peek out of boredom.
"A ball of Chakra? Could it be… he's going to train in Rasengan!?"
"Heh heh, although Rasengan is a crude imitation of the Tailed Beast Ball, it's not that easy to train."
Kurama scoffed, baring his stark white fangs in a grin.