Flying Thunder God Technique, Great Rasengan Wheel?

It was deep into the night. Namikaze Minato stood beside Kurama's claw, explaining things to Naruto.

"Naruto, you can't mark the Flying Thunder God formula on the giant iron gate of the seal space, even though it looks like a physical object..."

After leaving a message for Shikamaru, Naruto had gone straight home. There was no point in staying any longer.

Besides, according to what Shikamaru had said, he would be visiting Naruto frequently in the future to report to the Hokage. That made it even more inconvenient for Naruto to train the Flying Thunder God technique there.

After lunch, Naruto had been studying his father's signature jutsu, the Flying Thunder God, inside the seal space.

Hours passed, and Naruto was still contemplating the principles behind it.

The Flying Thunder God is a space-time ninjutsu.

In the ninja world, space-time ninjutsu is actually quite common—Summoning Jutsu, for instance.

Summoning Jutsu defies logic, allowing a ninja to form a blood contract with a summoned beast and teleport them to each other, disregarding spatial dimensions entirely.

Even Nagato had managed to summon the husk of the Ten-Tails from deep within the moon's core.

Naruto had seen plenty of such summoning feats in the Naruto anime from his previous life.

For example, in the early episodes, Jiraiya and Naruto could summon the toads of Mount Myoboku to Konoha. Later, Naruto himself could be reverse-summoned to Mount Myoboku by the toads.

Another application was storage scrolls—Naruto had two on him right now. Storage scrolls fall under the category of space-time ninjutsu as well, albeit in their simplest form.

A ninja could carry one, infuse it with chakra, and summon pre-stored tools from within. After use, the items could be sealed back inside.

Tenten was the prime example of using this technique.

Of course, in Naruto's opinion, the most powerful summoning technique was undoubtedly Edo Tensei (Reanimation Jutsu).

This forbidden technique, developed by the Second Hokage, could break the boundaries between life and death, exploiting loopholes in the cycle of reincarnation to summon the souls of the dead back into the living world.

Flying Thunder God, on the other hand, was a form of reverse summoning within space-time ninjutsu. However, unlike regular summoning, which required a blood contract, Flying Thunder God used chakra instead, and the contract was with oneself.

The entire process involved using one's own chakra to sense a marked formula, then teleporting oneself to that pre-marked location.

The Second Hokage had designed a unique summoning formula for the technique, incorporating elements of Body Flicker and Sealing Jutsu.

The most crucial requirement for mastering Flying Thunder God was an exceptionally high level of sensory perception.

Minato's three personal guards had failed to master the technique primarily due to their weak sensory abilities.

Individually, they couldn't accurately locate the formula markings they had set. As a workaround, they synchronized their chakra perception to the same frequency and worked together to barely manage the Flying Thunder Formation.

Thus, another prerequisite was that one must first place a marking within the desired teleportation zone.

The marking itself was formed using one's chakra. The moment it was placed, a sealing jutsu had to be cast simultaneously to solidify it.

That way, the coordinates would never fade. Minato had even emphasized this point to Obito during the Fourth Great Ninja War.

However, after Obito became the Ten-Tails Jinchuriki, he reconstructed his body, effectively erasing the Flying Thunder God mark Minato had placed on him.

From Minato's transferred memories, Naruto could tell that his father had struggled in the beginning due to a lack of guidance in understanding sensory perception and the formula markings.

However, Minato's natural talent was exceptional, and with the help of Uzumaki Kushina, he quickly grasped the fundamentals of Flying Thunder God by studying the vast array of Uzumaki clan sealing techniques and sensory training methods.

According to Minato, Naruto now possessed an overwhelming chakra advantage, had mastered sensory abilities, and had learned the core summoning formula for Flying Thunder God.

All that remained was the simple part—placing the mark at the desired location, sensing the chakra within it, and once resonance was achieved, the special reverse summoning formula would instantly teleport him there.

Once Naruto felt he had met the entry-level conditions for Flying Thunder God, he initially planned to challenge his father's data replica in the Mirror World to experience fighting against the technique firsthand.

However, he found that he couldn't challenge Minato's data replica—the system notified him that the relevant character data was incomplete.

Then, he attempted to mark the Mirror World's other battle puppets with the Flying Thunder God formula to use the technique in actual combat.

But whenever he and his shadow clones tried marking the puppets during a fight, the battle would inexplicably be forcibly ended.

The notification system kept spamming "Please complete the relevant data," as if it were broken.

Realizing that he couldn't train Flying Thunder God in the Mirror World, Naruto shifted his focus back to the seal space.

He found that kunai and other ninja tools could be projected into the space, and all the jutsu he knew could be used inside.

Then, he turned his attention to the giant sealing gate.

He tried various methods—the gate could be attacked with ninjutsu and even scratched with kunai, producing sparks.

Yet, for some reason, he couldn't imprint the Flying Thunder God formula on it.

That was when Minato explained that the iron gate wasn't a physical object but merely a visualization of the seal.

"Looks like I need to find a way to avoid surveillance first," Naruto thought, deciding to put Flying Thunder God training on hold for now.

After some thought, he walked up to Minato and said, "Father, let's work on adding nature transformation to Rasengan."

Minato's expression turned awkward. "Uh, Naruto, I actually spent my life researching that. I even consulted Jiraiya-sensei about it."

"But even Jiraiya-sensei, who also mastered Rasengan, couldn't figure it out. Later, I considered using Senjutsu to enhance chakra and see if I could break through the bottleneck. But by the time I learned Senjutsu, I was already Hokage, and my time in Mount Myoboku was too limited."

"You know what happened next—I never had the chance to delve deeper into adding nature transformation to Rasengan."

"So, in terms of this research, you and I are at the same starting point."

Hearing this, Naruto's heart sank. He knew that his father's idea of using Senjutsu was correct.

In the original series, Naruto struggled to infuse Wind Release into Rasengan, eventually developing the Rasenshuriken. But at that stage, it was only 50% complete.

It was unstable, required close-range contact, and had severe backlash effects.

Only after Naruto trained in Sage Mode at Mount Myoboku did the Rasenshuriken reach 100% completion—it became throwable, with no drawbacks.

Today just wasn't going well. One setback after another. Now his training plans had to be adjusted again...

"Heh~ Fourth Hokage, you're just overcomplicating things! Why not simply reinforce Rasengan further? Like how we Tailed Beasts condense chakra to form Tailed Beast Bombs—the more chakra, the stronger the blast."

Kurama suddenly propped himself up on one paw as he spoke.

Minato was momentarily stunned. Then he realized—unlike himself, his son had an Uzumaki's chakra reserves.

Naruto's eyes lit up. Kurama's idea made perfect sense. The original series had already introduced an upgraded version called Big Ball Rasengan.

Since Kurama had explained how Tailed Beast Bombs were formed, Naruto immediately put it into action. In an instant, a fist-sized Rasengan formed in his palm.

He started injecting more chakra into it.

Inside the seal space, the Rasengan swelled to the size of a soccer ball and kept growing.

A strange thought crossed Naruto's mind. He began compressing the Rasengan's density in the same way a Tailed Beast Bomb was formed.

Minato noticed something unusual and was about to speak, but Kurama held up a claw to stop him.

Naruto's Rasengan quickly shrank back to its original size. Then it turned black.

It was denser than anything he'd ever sensed. Around it, chaotic ring-like halos swirled, resembling planetary rings from sci-fi movies.

"What kind of Rasengan is this?"

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