Time flew by quickly during training and soon, ten days had passed.
During these ten days, Naruto not only fully mastered Wind Release nature transformation, but also learned the four different attribute Ninjutsu that Jiraiya had prepared for him.
Fire Release: Flame Bullet, Water Release: Wild Water Wave, Earth Release: Earth-Style Wall, and Lightning Release: Lightning Flash.
The ranks of the four Ninjutsu ranged from C-Rank to B-Rank. Although their power was not very great, to Naruto, their significance did not lie in their combat value.
To develop Chakra of other attributes, one needed to learn Ninjutsu of the corresponding attributes.
For example, by repeatedly using Fire Release Ninjutsu, the Chakra can flow and transform within the Chakra pathways according to the Fire Release nature transformation. The body will slowly adapt to the Fire Chakra form, eventually allowing one to control it with ease.
This process was extremely time-consuming for ordinary ninjas, and developing each new attribute required several months or even longer to let the body adapt to the new Chakra attribute.
But Naruto had fifty Shadow Clones training simultaneously, meaning what took others a month only took him half a day.
He completed the training for all four Ninjutsu given by Jiraiya in just two days. Although the power of the Ninjutsu unleashed using non-innate Chakra nature wasn't as strong, Naruto did not mind.
He wasn't aiming for the power of these Ninjutsu in the first place. What he needed was to use these Ninjutsu to gradually get his Chakra system to accept the four attributes of Fire, Water, Earth, and Lightning Chakra.
Ninjutsu was only the means, the attributes were the goal.
By the eleventh day, Jiraiya was starting to get impatient.
"Naruto, you can start practicing the Rasengan now."
Early in the morning, Jiraiya dragged Naruto out from the pile of Shadow Clones and shoved a water balloon filled with water into Naruto's hand.
"Your Wind Release nature transformation is already proficient enough, so now you can learn this."
"The training of the Rasengan is divided into three stages."
"The first step is rotation: use Chakra to make the water inside the balloon spin. The faster it spins, the better, until the water balloon is burst by centrifugal force."
"The second step is power: use the same method to spin a solid rubber ball. The requirement is to make the Chakra spin at high speed inside the ball without bursting it, and once you can crack the surface of the ball, you pass."
"The third step is maintenance: combine the first two steps to compress the Chakra into a stably spinning, high-density Chakra sphere with your bare hands."
"Complete these three steps, and an A-Rank Ninjutsu is yours."
After explaining these three steps, Jiraiya asked, "Do you know why we practice with balls first?"
"Because it's currently very hard for your Chakra to maintain a stable rotation without a container. Creating it directly with your bare hands is purely theoretical. Most people get stuck on the first two stages for a very long time."
After Jiraiya finished speaking, he looked at Naruto, only to see him support the water balloon with his right palm, and pour Chakra from his palm into the balloon.
The moment the Chakra was injected, the water balloon began to spin at high speed centrifugally. The water balloon lasted less than three seconds in Naruto's palm before its inner wall was torn to shreds by the centrifugal force of the rotation, splashing water all over his hand.
Naruto looked up at Jiraiya, and said with a hint of uncertainty in his tone, "Pervy Sage, this doesn't seem very hard."
Jiraiya fell silent.
His mouth opened and closed, but in the end, he said nothing, walking away.
Half an hour later,
Jiraiya walked back holding a solid rubber ball, preparing to hand the training prop for the second step to Naruto, while repeatedly mentally preparing himself.
Even if Naruto got through the first step quickly, this tough second step would definitely keep him practicing for a while.
Then he saw Naruto sitting on the edge of the platform, his right palm spread open facing upward, as a blue Chakra sphere spun at high speed in his palm.
The rubber ball in Jiraiya's hand slipped out and rolled to a stop right at Naruto's feet.
"You... Naruto, are you a monster?"
Naruto dispelled the Rasengan and looked up at Jiraiya's thunderstruck face, smiling. "Pervy Sage, this doesn't seem hard."
"The first step is rotation, the second is power, and the third is maintenance. Maybe it's because I've already seen this Ninjutsu in a dream before, though I didn't know the training method back then."
"Now that you've explained the trick to each step in detail, I was able to perform it very quickly."
Jiraiya fell silent.
Minato had spent three years developing this technique, yet Naruto had spent less than a morning to learn it.
Jiraiya pulled out a summoning scroll and unfurled it in front of Naruto. A long list of signatures was lined up on the scroll, each name written in blood, with the newest and most prominent signature being Minato.
"This is Mount Myōboku's summoning contract."
Jiraiya flattened the scroll in front of Naruto and said, "Write your name on it using your own blood. Once your name is written, you will be an official contractor of the toad clan of Mount Myōboku."
"Remember, this contract is not a tool for unilaterally summoning ninja beasts. It is proof of the bond between you and the toad clan."
"Which toad you summon later depends on how much you can summon, whether the toads are willing to help you, and most importantly, your own Chakra levels."
As Naruto looked at the name of Minato on the scroll, his finger paused involuntarily.
'Sage Mode, huh?' Naruto muttered to himself in his heart.
Then he bit his right thumb and wrote two words: Uzumaki Naruto.