The afternoon sun filtered gently through the leaves as Kakashi's curiosity finally got the better of him. He turned toward Minato, who was resting beneath the shade of a large tree, a faint smile playing on his lips. Kakashi had heard whispers from his sister, Kushina, about a new ninjutsu Minato was developing—a technique that had been in the works for three long years.
"By the way, Minato-sensei," Kakashi began casually, "I heard from Sister Kushina that you're working on a new kind of ninjutsu. A 'Muji Ninjutsu,' was it? Could you show it to me?"
Minato's smile became a little sheepish as he scratched the back of his head. "Ah, that... I haven't quite finished it yet."
Kakashi's interest piqued. In the original stories, Naruto had learned the Rasengan—a technique Minato spent years perfecting—in just a matter of days. This discrepancy made Kakashi all the more curious about the true development process.
Noticing Kakashi's eager gaze, Minato lifted his right hand, and with a subtle movement, a shimmering blue sphere of chakra hovered above his palm. It pulsed faintly, glowing with a mysterious energy.
"Minato-sensei, are you just compressing your chakra into a sphere?" Kakashi asked thoughtfully, eyes narrowing.
He recalled the theory from his studies: simply compressing chakra forcibly into a ball would likely cause an unstable internal structure. And when such a sphere explodes, wouldn't the user also suffer damage?
"This ball... wouldn't it be dangerous if it detonated?" Kakashi asked.
Minato nodded, a hint of concern crossing his face. "Yes, that's exactly the problem. This sphere isn't stable yet. If it explodes too close to me, I'd definitely be hurt."
Kakashi considered the ball carefully. The shape resembled the Tailed Beast Bomb, a technique used by the enormous Tailed Beasts—immense balls of chakra compressed to a near-nuclear level. But unlike those colossal creatures, humans don't possess nearly enough chakra or the ability to compress it so tightly without losing control.
"You see," Minato explained, "the Tailed Beast Bomb is something only the Tailed Beasts can create. Their chakra is so vast and powerful that it can cause massive destruction. For us humans, trying to imitate that directly is impossible."
Kakashi's mind raced as he recalled the teachings of Jiraiya and the stories he'd heard from Naruto.
"But if you just compress the chakra tightly and throw it, won't the sphere become unstable and dissipate before it hits the target?"
"Exactly!" Minato said, nodding vigorously. "If I throw this unstable sphere, it scatters mid-flight and loses power quickly. If I try to make it stable by reducing the chakra weight, it loses its destructive force."
Kakashi tapped his chin. "What if you rotate the chakra within the sphere, in the same direction as the body's spin, to create a dynamic balance?"
Minato's eyes suddenly lit up. "Why didn't I think of that? Kakashi, you're a genius!"
Without hesitation, Minato began experimenting again. His fingers moved quickly, channeling chakra with newfound intent. Three minutes later, a new blue sphere formed, more compact and vibrant than before.
Minato vanished in a flash and reappeared beside a thick tree trunk. With a confident smile, he pressed the sphere against the bark.
There was no explosion.
Instead, the sphere cut through the wood like a drill, gouging a deep hole clean through the tree trunk.
"That's it!" Kakashi exclaimed inwardly.
Minato smiled broadly. "This is the Rasengan!"
Kakashi nodded approvingly. The power, the precision—it all aligned with what he expected from such a technique.
He thought to himself: This development speed matches Minato's talent perfectly. The reason it took so long in the original stories must have been a misunderstanding of the right approach.
Rasengan was, after all, the pinnacle of chakra shape transformation—an ability Minato had mastered through intense training.
"Since you came up with this so fast, why don't you give it a name?" Minato asked excitedly. Naming techniques was one of his favorite hobbies.
He waved his hand and chuckled. "I could suggest names like Spiral Flash Turbo Zero or Visiting Wind—those sound pretty cool, right?"
Kakashi laughed and quickly interrupted. "How about we just call it 'Rasengan'?"
Minato paused for a moment, considering the word. "Rasengan... It sounds simple but powerful."
Kakashi grinned. "Yes, and it's easier to shout in the middle of battle!"
Minato seemed satisfied but then furrowed his brow thoughtfully. "Still... I think there's more to improve."
Before Minato could continue, Kakashi seized the moment to change the subject.
"Actually, Minato-sensei," he said casually, "I recently developed a new technique. Would you like to see it?"
Minato's curiosity was instantly piqued.
"Of course! Show me," he said eagerly, standing up.
Kakashi formed hand signs smoothly. Suddenly, arcs of crackling electricity appeared around his right hand, crackling and humming with raw energy.
"Ox-Rabbit-Monkey," Kakashi chanted as his fingers danced through the seals.
With a sudden shout, "Chidori!" a brilliant flash of lightning surged from his palm, expanding rapidly into a glowing mass that crackled with overwhelming power.
The light was so intense that birds nearby took flight in panic, their chirps rising to a crescendo.
Minato's eyes widened in awe. "What is that?!"
Despite his experience and skill, Minato had never seen such a technique before. The sheer intensity and danger radiating from Kakashi's hand told him this was no ordinary jutsu.
"This... This must be a powerful ninjutsu—maybe as strong as the Rasengan!" Minato said, shaking his head in disbelief.
Kakashi shrugged, a casual smile on his face. "Yeah, I came up with it pretty quickly. Took about a week to develop."
Minato was speechless. He had spent two months creating the Rasengan, and it was only with Kakashi's timely advice that he had finally broken through the critical barrier. Meanwhile, Kakashi had managed to invent a high-level A-rank technique in just seven days.
Who really is the teacher here? Minato mused with a mixture of admiration and playful envy.
But he quickly shook off the shock. "Well, the better your students, the better teacher you must be," he said, regaining his usual optimism.
"No wonder you wanted to train your reaction speed with me all this time," Minato added, narrowing his eyes knowingly.
Kakashi laughed. "You caught me."
Minato nodded thoughtfully. "I was originally planning to teach you the Rasengan so you could use it alongside the Flying Thunder God technique."
"Now I see you've already started walking your own path."
"Perhaps it won't be long before you surpass me entirely."
His voice softened, and a rare note of pride entered his tone.
At that moment, Kakashi raised his left hand, forming a small glowing sphere similar to the Rasengan but slightly different—a perfect miniature swirling orb of chakra that pulsed with energy.
"Actually, Minato-sensei, I've already learned the Rasengan."
Minato blinked, stunned.
In all his years as a mentor and ninja, he had never seen a talent like this.
Many gifted individuals had come and gone, but none possessed the sheer aptitude Kakashi displayed for ninjutsu.
This is extraordinary... Minato thought. Maybe this young man is destined to become Hokage himself.
"Minato-sensei? Are you still with me?"
Kakashi's voice cut through his reverie.
"Oh! Sorry, I was distracted for a moment," Minato said, smiling sheepishly. "I'm just... impressed."
He looked at Kakashi with a renewed sense of hope and expectation.
Kakashi nodded and continued, "I was thinking—since Rasengan represents the ultimate form of chakra shaping, and Chidori is the pinnacle of lightning chakra nature transformation, could the two be combined?"
Minato's expression darkened with serious contemplation. "A fusion of the two?"
He sighed deeply. "Rasengan is indeed the ultimate expression of chakra manipulation."
"Your Chidori appears to be the highest level manifestation of Lightning Release."
"If you combine them, you're not just mixing techniques—you're attempting to create an S-rank ultimate killing jutsu."
"The difficulty will increase exponentially. Even I cannot guarantee success."
He paused and looked directly at Kakashi.
"I don't recommend you attempt this on your own—it's far too dangerous."
"If you insist on trying, you must swear that I'll be there to supervise."
Kakashi felt a warm surge in his chest.
Beneath Minato's stern words lay deep care and genuine concern for his student's safety.
"Absolutely, Minato-sensei," Kakashi said with a firm nod.