Below the rooftop, Kakashi Hatake was still eavesdropping on the kids' conversation. When he heard about the duel between Naruto Uzumaki and Sasuke Uchiha, he simply frowned.
Kakashi clearly had no intention of stopping them. Or rather, he wouldn't intervene unless they were in real danger. This was a good chance for him to observe the strengths and weaknesses of the two boys. After all, until Sakura Haruno matured as a ninja, Naruto and Sasuke would be the main combat power of Team 7.
"Naruto, are you really going to fight Sasuke?" Sakura asked, looking at the two boys standing opposite each other. "Sasuke was always number one at the Ninja Academy! And you were always..."
"The dead-last, right?" Naruto grinned, flexing his fingers. "Even a dead-last has the heart of a top student!"
He had challenged Sasuke many times during their Academy days. Now that he had mastered a few new ninjutsu, he was eager to test his own strength. In their entire class, no one was a better benchmark than Sasuke Uchiha.
Besides the basic techniques from the Academy, Naruto now had four new jutsu. Aside from the still-unfamiliar [Sealing Art: Devour], the other three—[Rasengan], [Wind Style: Rasenshuriken], and [Multi-Shadow Clone Technique]—felt as natural as if he'd been using them his whole life.
"Here I come, Sasuke!" Naruto shouted and rushed forward.
Sasuke blocked his flying kick with one arm, then twisted his body and kicked back at Naruto's stomach. The two boys instantly fell into a flurry of blows, their fists and feet clashing. It was clear a fire had been lit between them.
Only Sasuke knew that Naruto's taijutsu was already much better than it was at the Academy. He'd improved so fast.
Sasuke glanced at Naruto's hand and, with a quick thought, clamped his own fingers down to restrain it. Just as he was about to make his next move, Naruto chuckled. "Ha, Sasuke. Trying to use my hand to help you form hand seals?"
"Hmm?"
Sasuke was stunned for a moment, and Naruto used the opening to pull his hand free. Sasuke's mind was still reeling, trying to figure out how Naruto had seen through his move.
In the middle of a fast-paced taijutsu battle, it's almost impossible for a ninja to find time to form hand seals for a jutsu. To get around this, some shinobi have developed unusual methods for seal formation. Using an enemy's hand to help complete your own hand seals during a clash could save precious time and catch them completely off guard.
Besides his diligent practice of ninjutsu and shurikenjutsu, Sasuke occasionally looked for shortcuts. To him, any opportunity to become stronger was one he couldn't afford to miss. He had only just begun learning the [Borrowing a Hand for Hand Seals] technique and could currently only use it for the Great Fireball Technique. He had planned to test it on Naruto, but he never expected Naruto to see through it instantly.
Perhaps this move wouldn't work after all.
"That's a terrifying technique," Naruto said with another kick. "Using the enemy's fingers to form hand seals. If someone didn't realize what you were doing, I bet they wouldn't be able to react, right?"
"Hmph!" Sasuke raised his arm to block the kick, his brow furrowing. The heavy force almost knocked him to the ground. Ever since their Academy days, every time he fought Naruto, he could feel the kid's strength growing. Even though he was from Konoha's once-proudest clan, he had to rely on pure skill to counter Naruto's raw power.
This dead-last was more troublesome than before. No, it should be said, he had really gotten stronger.
Sasuke brought his arms together, blocking a punch from Naruto. He didn't even need to look to know his arm must be turning red.
His form is still sloppy like the dead-last he used to be, Sasuke thought, glancing at Naruto's confident smile, but every so often he pulls off a perfect attack, almost like it's muscle memory... This guy was never very diligent in the Academy...
Naruto scratched his yellow hair and grinned. "Ha, maybe I don't work as hard as the top student, but I won't let myself fall too far behind, either."
It was true. In their entire class, no student was more diligent than Sasuke Uchiha. Perhaps because he carried the hatred of his clan on his shoulders, Sasuke never gave up an opportunity to train.
Naruto, on the other hand, was different. He often skipped his theory classes. Besides basic taijutsu, his chakra control was poor, and he couldn't even perform simple D-rank ninjutsu. That all changed the day he used the strange forbidden jutsu, [Sealing Art: Devour], to swallow the red chakra in his sealing space. The Nine-Tailed Fox became obedient, and suddenly Naruto could use ninjutsu proficiently.
His taijutsu skills had also strangely improved. He could now instinctively see an opponent's opening and launch a counterattack. He clearly hadn't experienced many battles, but it was now second nature to him.
"I have to admit, I really underestimated you in the past," Sasuke said, squeezing his sore wrist. "But true strength isn't built overnight!"
His palms suddenly came together, forming hand seals.
Serpent—Ram—Monkey—Boar—Horse—Tiger!
Chakra condensed in Sasuke's chest, which swelled slightly. He brought his fingers to his mouth and unleashed a massive fireball. "Fire Style: Great Fireball Technique!"
The flames expanded rapidly, shooting towards Naruto.
At a window in the Ninja Academy, Asuma Sarutobi, who was watching the fight, looked on in surprise. "As expected of the Uchiha clan, huh? To be able to use a C-rank Fire Style jutsu so skillfully at this age..."
"It's rare for a graduate to reach this level," Kurenai Yuhi added, nodding seriously. "He may be a bit inferior to his older brother who defected, but he's more outstanding than most students."
Asuma suddenly realized the danger. "Wait, a jutsu of this level could be dangerous..." he said, about to jump out the window.
"Hey, hey! Calm down, Asuma!" Kurenai pointed to Kakashi, who was already on the railing. "Don't worry, Kakashi is moving to save them."
Kakashi, who had been eavesdropping the whole time, had finally decided to intervene when he heard Sasuke begin the Great Fireball Technique. But after hopping onto the rooftop, he saw a scene that made his mask almost fall off in shock.
The smile on Naruto's face didn't fade. As the flames approached, he extended his palm. "Sealing Art: Devour!"
He completely devoured the chakra of the Great Fireball Technique. The scorching heat vanished without a trace.
"Sasuke, your hand seals are too slow!"
A Rasengan abruptly appeared in Naruto's palm. He then charged at Sasuke. "Rasengan!"
"Wait!" Kakashi watched Naruto rush forward, and for a moment, he saw the shadow of another person in him. He was momentarily stunned.
In the distance, Asuma shouted, "Hey, Kakashi, what are you doing! Hurry up and stop those two!"
Kakashi snapped back to reality and quickly grabbed Naruto's arm, slamming the Rasengan into a nearby retaining wall.
Boom!
The wall collapsed instantly, sending rubble clattering to the ground.
Kakashi took a deep breath and gave Naruto a weary look. He rubbed his neck and tried to act nonchalant. "Hey, the Rasengan isn't something you should be learning at this age. When did you pick that up?"
"A few days ago at the training grounds," Naruto said, looking a bit dissatisfied. "I developed it myself. With this jutsu, I can definitely defeat Sasuke!"
"Hmph!" Sasuke couldn't help but snort, but when he saw the obliterated wall, the corner of his eye twitched.
That jutsu, the Rasengan, was incredibly powerful. It might have some flaws due to its limited range, but if it hit him, it would definitely be a one-shot victory. Sasuke looked up at Naruto, the school's dead-last. Had he really gained this kind of strength without anyone noticing?
Looking at it this way, Naruto was much stronger than the girl, Sakura. He probably wouldn't drag the team down. But to avoid being surpassed, Sasuke knew he also had to learn a stronger jutsu.
Just as Naruto was looking smug, Kakashi's calm expression almost broke. "The Rasengan is the Fourth Hokage's signature ninjutsu. Kid, there should be a limit to your lies! In the entire ninja world, not many people know that jutsu better than I do."
"Huh? The Fourth Hokage's jutsu?" Naruto looked up in surprise. He pondered for a moment, and chakra began gathering and rotating in his palm again. "Then is this Wind Style: Rasenshuriken also the Fourth Hokage's jutsu? Because I really did develop this one myself!"
As he poured more chakra into it, wind-natured chakra mixed in, and the Rasengan gradually transformed into a constantly rotating, shuriken-shaped vortex of energy.
"...This is..." Kakashi's heart trembled. The Rasengan, mixed with wind-natured chakra, had completely changed its form, becoming a diamond-shaped shuriken. This was even more dangerous than the Rasengan.
No matter how you looked at it, this was not a jutsu a genin should have mastered. Especially not Naruto, who had just graduated as the school's dead-last.
As the student of the Rasengan's creator, Kakashi was extremely knowledgeable about the jutsu. But because of his own limited chakra, he never dared to be so extravagant with it. The key point was this: not even the Fourth Hokage had ever managed to add a nature transformation to the Rasengan.
"To become Hokage, to surpass the Hokage..." Kakashi's gaze fell on Naruto's face, and he muttered to himself, "At this age, has he already surpassed his master in the art of the Rasengan?"
"Hah, of course!" Naruto interrupted Kakashi's thoughts, holding up the Rasenshuriken. "Since you're here, Kakashi-sensei, you're obviously not going to let me and Sasuke continue our fight, right?"
"Of course..." Kakashi took a deep breath and nodded. If he let Naruto throw that Wind Style: Rasenshuriken, the last seedling of the Uchiha clan would probably go extinct.
-----
Bonus:
Underworld Headline 1: "Rasengan Caught in Copyright Dispute: Who is the Real Inventor?"
Underworld Headline 2: "Minato Namikaze in Plagiarism Scandal? The Genius Boy's Rasengan Nature Transformation!"
Underworld Headline 3: "Fourth Hokage States: 'I have been dead for twelve years, while the plagiarist is only twelve years old!'"
Underworld Headline 4: "Minato Namikaze Retracts Statement: 'Perhaps it was a meeting of minds; I am willing to give up the Rasengan copyright!'"
Underworld Headline 5: "A Grand Drama of Fame, Fortune, and Inheritance: Minato Namikaze is Actually the Plagiarist's Father! Why Did He Give Up the Rasengan Copyright?"
Minato Namikaze: Second Hokage, can you please shut down your little newspaper?
Tobirama Senju: Excuse me, are you giving up the Rasengan copyright because you want to establish a feudal system of father-son succession in Konoha?
Minato Namikaze: As if your family's brother-to-brother succession is so noble...
Tobirama Senju: ???