Everyone regathered, and Kitagawa said, "Everyone just witnessed it. If we treat Gai like that small ball, it's the same phenomenon I showed at the start."
"The ball didn't fly away because of the string, and it kept rotating."
"When I released Gai, he flew away."
Kushina looked confused. "So Kitagawa, what exactly are you trying to say?"
Shizune was also confused. Gai was completely lost. Jiraiya and Tsunade were deep in thought.
Kitagawa looked at Minato. "Minato, what do you think?"
Minato pondered, "The string prevented the ball from flying away. Just now it was because you held Gai's hand. I think you're trying to convey that some kind of force contained the ball or Gai, preventing them from flying away. Is that right?"
Kitagawa smiled. "Exactly."
"The string and my grip on Gai are just surface phenomena. The hidden force underneath is the fundamental principle."
"I held Gai, so he didn't fly away. Why? Because I applied force to him. When I released him, he flew away. Why is that?"
Kushina instinctively countered, "Isn't it because you held Gai firmly?"
Shizune and Gai both nodded in agreement.
Kitagawa laughed. "Right, because I held Gai. But why could I hold Gai?"
Kushina got black lines on her head. "Kitagawa, I now think you're a very qualified teacher."
"Hahaha~"
Kushina bent over laughing, hands on her hips.
Kitagawa spread his hands. "Well, it's probably a teacher habit."
He looked at Minato. "High-speed rotating chakra creates friction force that causes damage, right?"
Minato nodded.
Kitagawa pressed his palms together, then slowly pulled them apart. "Palms rubbing together—friction is produced."
"When I held Gai and he didn't fly away, friction was also at work."
"Why do humans fall after jumping into the air? Because of Earth's gravity."
"As Jiraiya-sama said earlier, we can't use string to bind rotating chakra, nor can we grab chakra with our hands."
"So how do we keep chakra rotating without scattering outward? We need some force to constrain it."
"Like friction. Like Earth's gravity!"
Kitagawa crouched down and pulled out prepared paper and pen. Before everyone's eyes, he marked a very obvious point.
"Minato, assume this is the core point of the chakra sphere. The center."
As Kitagawa spoke, he drew circles around the point. "This circle is the rotating chakra."
Next, he quickly drew—overlapping circular lines repeatedly, eventually forming a sphere shape on the paper.
Kitagawa pointed at the sphere. "This is the chakra sphere. Each line is rotating chakra."
"Chakra rotating in different directions will have friction with each other, producing friction force. Meanwhile, they're also affected by gravity."
"Because directions differ, the friction forces differ too. All these forces combined can offset the dispersive force of chakra, maintaining the sphere's integrity."
Minato's eyes lit up brilliantly. "I see! Kitagawa, you're a true genius!"
Kushina looked baffled. "Minato, you understood?"
Minato nodded.
Jiraiya also understood. Though he didn't quite grasp it all, he nonetheless had a minor complaint. "Kitagawa, you could've just directly told us—just make the chakra rotate in different directions, right? Why all the trouble?"
Tsunade snorted coldly. "Idiot Jiraiya. If he just told you directly, how would you understand why this method works to maintain the chakra sphere?"
Jiraiya quickly shouted, "How could I not know? I understood Kitagawa's meaning from the start!"
Tsunade couldn't be bothered with him, simply snorting with contempt. "Tch."
Jiraiya cleared his throat and then said to Minato, "Minato, try it now!"
Minato nodded and immediately placed his hands in a cupping position. Chakra began condensing.
Kitagawa quietly observed.
All that verbose explanation was essentially the formula: Active Force + Constraint Force + Fictitious Inertial Force = 0.
The active force drives chakra rotation. The constraint force is the combined effect of friction, gravity, etc. The fictitious inertial force is the dispersive force of chakra.
Of course, specific to the Rasengan technique itself, the key point was that initial dot Kitagawa marked when drawing.
The chakra sphere's core.
But Kitagawa believed Minato would definitely understand.
"Success!"
Kushina's cheer brought Kitagawa back to attention.
Between Minato's hands sat a brilliant blue chakra sphere.
Tsunade looked at it seriously. "Such high-density chakra—the power is definitely extraordinary."
"And this seemingly irregular chakra rotation with such high-difficulty form transformation—rating it A-rank is entirely justified."
Kitagawa smiled. "Tsunade-sama, it's not actually irregular rotation. Though rotating in different directions, they actually share one core point."
"That's also a critical aspect of this technique."
"In essence, all rotating chakra converges toward this core point."
This could actually be described using centripetal force!
Kushina cheered, "Minato, hurry and test the power of this technique!"
Minato nodded. "Everyone, step back a bit."
Everyone retreated.
However, just as Minato was about to test it, the sphere in his hands suddenly scattered.
"Ah..."
Minato looked embarrassed. "Still not practiced enough."
Kitagawa laughed, "At least you've completed the technique. Now you just need more practice to use it in actual combat."
Minato quickly said, "All thanks to you, Kitagawa. This technique wouldn't have been completed without you."
Kitagawa smiled, "And I have to thank you for believing in me."
Gai's eyes were full of admiration. "I told you Teacher Kitagawa is the strongest teacher!"
Kushina patted Gai's shoulder. "I think so too now. Though it would've been better if the explanation wasn't so verbose. Hahaha~"
Shizune, as Kitagawa's student, felt a sense of pride. "As expected of Teacher Kitagawa. In such a short time, he developed an A-rank no-seal ninjutsu."
Though the technique came from Minato's concept, Shizune felt it was Teacher Kitagawa who perfected it.
Gai was right—Teacher Kitagawa really is the strongest teacher!
Jiraiya, who'd previously boasted about being the strongest teacher, quickly said, "Minato, give this technique a name!"
Minato said, "Kitagawa, why don't you name it? Your contribution was greatest."
Kitagawa shook his head. "It's your technique, Minato. I just offered some input. You should name it!"
Kushina, being impatient, quickly said, "You two stop being modest! Each suggest one, and whoever's is better gets used!"
Kitagawa and Minato exchanged glances, then both nodded.
"Mine would be..."
Minato pondered briefly, then smiled. "Halo Friction Rotating Kitagawa Dual-Sphere!"