Minato's expression turned solemn, his smile replaced by intense focus. He stared at his raised right palm, murmuring to himself as if solving a complex academic problem:
"I think I understand why it failed!"
"To make the Halo-Cat-Paw-Counter-Return-Inspired-Whorl-Uchiha-Dual-Style-Sphere produce an explosion—"
Ren couldn't help but twitch his lips. "I told you, stop using that name!"
The brief retort didn't affect Minato's concentration. However, when Minato spoke his next thought, Ren's expression sharpened, and he listened intently.
A deep blue orb appeared in Minato's palm. Unlike a normal Rasengan, this one was darker in color, and the moment it manifested, it began to expand rapidly, its surface becoming extremely unstable.
"I've got it!"
Minato raised an eyebrow, his eyes locked on the expanding sphere. "The key point isn't the violent chakra rotating around the center!"
"It's the core point itself. Just like you said, Ren—you have to suppress the chakra that bulges out of the sphere to stabilize it. Previously, because I was unconsciously mimicking a Tailed Beast, I compressed the core point too much, which caused the surrounding chakra to rotate even faster until it spiraled out of control and expanded!"
"So, the critical core—"
"Lies in the compression! Compressing the nucleus of the Halo-Cat-Paw-Counter-Return-Inspired-Whorl-Uchiha-Dual-Style-Sphere!"
Watching the Rasengan in Minato's hand grow so fast it was on the verge of detonating, Ren's eyes widened. In that instant, it was as if he'd had a moment of pure enlightenment!
Minato was truly the pioneer of the Rasengan. After completing the normal form, he had immediately reverse-engineered the cause of the failure. When it came to "spherical" problems, the creator really did have the fastest answers!
Because Minato had witnessed the Tailed Beast Bomb, his initial design was benchmarked against it, leading to this prototype. Compress the core, increase the centrifugal force, and drive the chakra into a violent state of rotation until it becomes uncontrollable and expands!
From Minato's words, Ren quickly thought of another variant of the Rasengan—one used by Menma Uzumaki in the Road to Ninja movie:
Spiralling Ring (Rasennringu)!
The principle was also compression, but it involved compressing the rotating outer chakra along with the core. Its advanced version, the Great Spiralling Ring, had a destructive range no less than the Almighty Push (Shinra Tensei) used by Pain! A single strike could level Konoha!
Minato's eyes lit up again. With his high intellect, he immediately made the connection to a similar principle.
"If I compress both the core and the outer chakra together... this form of the Halo-Cat-Paw-Counter-Return-Inspired-Whorl-Uchiha-Dual-Style-Sphere... well, perhaps it could be stabilized?"
"And the power... it seems it could be increased even further?"
Ren fell silent, unsure how to answer. Increased? Of course it could be increased—that's literally the Great Spiralling Ring!
Wait, what have I done? Ren thought. Under my influence, is Minato going to develop a movie-exclusive ultimate move? This is bad... "Blue-Flash" Minato is getting a massive buff!
If Minato used Flying Raijin to teleport above an enemy village and dropped a Sage Art: Great Spiralling Ring... the image was so terrifying Ren didn't even want to contemplate the consequences. Not to mention the "A-B Brothers" (A and Killer B) who would soon face Minato—how big would their psychological trauma be when their rival pulled out a literal nuke?
However, as the two were lost in their theoretical discussion, a voice called out from the distance.
"Minato-sensei! Ren-san! It's time to start cooking!~"
Rin Nohara waved from afar. The three students had returned with gathered wood and wild vegetables. But as soon as they looked up, they saw their teacher standing there with a violently expanding, unstable blue orb in his hand, casually chatting and laughing with Ren while ignoring the fact that it was about to blow.
The sheer absurdity of the scene left the three of them stunned. Obito dropped his bundle of dry branches with a clatter and screamed in terror:
"Sensei! Ren!!"
"It's gonna blow! It's gonna blow, ahhh!"
"Huh?" Minato blinked, then looked at the nearly detonating sphere in his hand. His pupils shrank. He vanished instantly, reappearing at a Flying Raijin marker 200 meters away, hurled the expanding Rasengan, and flickered back to the haystack.
BOOM!
The expanding Rasengan, which had been infused with a massive amount of chakra, exploded into a miniature pillar of light. A gale swept past them, carrying soil, grass, and broken branches through the air.
"What was that?!" Kakashi and the others stared wide-eyed at the crater.
Minato exhaled, scratching his head with a sheepish smile. "Well, it's just a new jutsu I'm working on. It's still pretty dangerous—liable to explode at any time." He turned to Ren. "Ren, let's talk more about the jutsu after we get back to the village. For now, let's eat."
Ren nodded. He had learned the principle of the expanding Rasengan and mastered the base version. He had gained a lot, and he assumed Minato had too.
As for controlling Dark Chakra, combining it with Sage Art, and refining the "Man-Made Tailed Beast Bomb," he would have to solve those on his own. Besides, Ren had a feeling that training this technique would be... loud. This wasn't the right place for it.
Regarding the "compression" of the core that Minato mentioned, Ren already had a lead. The inspiration came from a skill he had gained after slaying Ebizo.
He narrowed his eyes and pulled up his status panel, scrolling through the recent notifications:
[Ding!]
[You have bravely defeated Ebizo, the supreme commander of the Sand who sought to kill you. You have obtained a random skill from the target: Human Puppet Technique: Creation of the Regeneration Core (A-Rank, Entry).]
[The counter-attack was significant; the target is dead and cannot object. Reward has triggered a Critical Hit.]
[Skill Critical Hit: Current attribute is now: Human Puppet Technique: Creation of the Regeneration Core (A-Rank, Proficient).]
[Your Heartsteel stacks have increased.]
Human Puppet Technique: Creation of the Regeneration Core!
This was the precursor technique used by Sasori of the Red Sand to achieve his "eternal art." Sasori turned himself into a human puppet and modified his heart into an eternal chakra regeneration core to achieve a unique form of immortality.
The key to all of that was this technique!
It was the forbidden art of modifying the deceased into human puppets, condensing a chakra core, and manipulating all the abilities they possessed in life.
Ren figured... if you can condense the chakra of the dead into a core, it's clearly a high-end compression technique.
Surely it works on the living, too?
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