On the training grounds, Fumori masaki and Namikaze Minato were practicing the Flying Thunder God Technique. Fumori masaki was still just a shadow clone at this time; not only did his main body have administrative duties to attend to, but it was also better to train with a "Fumori masaki" whose power was restricted.
After all, no matter how powerful Namikaze Minato would become in the future, he was still just a young man at present, far from his prime.
Even the Fourth Hokage from another timeline probably couldn't defeat Fumori masaki, let alone the seventeen-year-old Namikaze Minato of today.
However, after studying under Fumori masaki, Namikaze Minato's strength indeed grew rapidly. Also, due to entering his growth spurt, his height shot up like a bamboo shoot absorbing nutrients, and he was now a young man.
Standing in front of Fumori masaki, Namikaze Minato tightly gripped a specially made Flying Thunder God kunai. Its three-pronged shape made it heavier and more powerful than a regular kunai, and when infused with wind-style chakra, its destructive power was extraordinary.
Namikaze Minato stared at Fumori masaki, reached into his ninja tool pouch, and flung out a large number of Flying Thunder God kunai. However, as they approached Fumori masaki, they seemed to be blocked by an invisible wall, missing him and landing elsewhere.
Namikaze Minato already knew that this couldn't harm Fumori masaki; he merely needed the landing points of the Flying Thunder God kunai to expand his movement range.
Of course, if Fumori masaki wanted to, he could completely destroy all the kunai with his Wind Release. He had the strength, even a shadow clone with half his power could do it, but that would be too unfair to a young man like Namikaze Minato.
The age, experience, and strength gap between them were evident. If Fumori masaki were always serious, Namikaze Minato would have no chance of winning, which would defeat the purpose of training. The ideal standard was to be slightly stronger than Namikaze Minato's current strength, providing him with a sense of pressure while also allowing him to utilize his abilities and find ways to defeat him.
It was like surpassing his limits step by step. Although Namikaze Minato had never won against Fumori masaki in all these years, his strength had improved and surpassed itself in battle after battle.
Namikaze Minato was very clear about the weaknesses of the Flying Thunder God Technique. The Flying Thunder God's movement required a jutsu formula; without a jutsu formula as a marker, spatial movement couldn't occur. His teacher also understood this, so the main purpose of the training was how to successfully mark Fumori masaki's back with the Flying Thunder God's seal through layers of defense, thereby achieving a one-hit kill.
Fumori masaki possessed sensory abilities comparable to the precision of the Sharingan, along with powerful Wind Release and the ability to use natural energy remotely. Marking him with the Flying Thunder God Technique through such defenses was exceptionally difficult. Conversely, if Namikaze Minato could successfully mark him under such circumstances, his strength would undoubtedly become formidable.
After layers of "ability unlocking" through combat, the strength Fumori masaki could now exert was such that ordinary methods could no longer be used for Flying Thunder God marking.
This was also where Fumori masaki intentionally trained Namikaze Minato. In his previous life, people had studied Namikaze Minato's fighting style, and the conclusions were basically consistent: he was extremely fast and posed a huge threat to ninjas with high offense and low defense. However, when encountering ninjas with strong defensive capabilities, he was like hitting a brick wall. In short, he was a high-speed, low-attack assassin-type fighter.
It's not that Namikaze Minato couldn't perform powerful ninjutsu, but for him, whose primary combat method was the Flying Thunder God, complex hand-seal ninjutsu would, to some extent, slow down his combat rhythm and hinder the effectiveness of the Flying Thunder God Technique.
The Fourth Hokage in the original timeline also realized this, which is why he developed the Rasengan, a ninjutsu without hand seals. As an A-rank ninjutsu, the Rasengan's power was already terrifying, and most people in the ninja world could not withstand its impact. The fact that it didn't require hand seals also made it very suitable for the Flying Thunder God Technique.
Although there were individuals with iron-hard bodies like the Third Raikage, the Third Raikage was an anomaly and couldn't be generalized. Furthermore, if that Fourth Hokage hadn't died in the Nine-Tails incident and had completed the great feat of adding nature transformation to the Rasengan, a wind-style Rasengan or Rasenshuriken would have been remarkably effective against a living Third Raikage.
Even if it didn't knock him down in one hit, the Fourth Hokage could land several blows. Since the Third Raikage, not being an Edo Tensei body, couldn't heal his injuries, as long as the Fourth Hokage had enough chakra, wearing down the Third Raikage was entirely possible.
Considering this, by the time the Fourth Hokage reached his thirties, there might have been virtually no one in the entire ninja world who could defeat him. Only those at or above Pain's level might have been able to suppress him, but even that was uncertain, as the extent of the Fourth Hokage's growth by then was unimaginable given his talent.
No wonder Jiraiya regarded the Fourth Hokage as the new Child of Prophecy after Nagato, the "Sage's reincarnation." The Fourth Hokage, from a commoner background, was able to overpower most of the strong individuals in the ninja world, including those from bloodline limit clans, making it impossible not to entertain such thoughts.
Fumori masaki even wondered if Namikaze Minato had some powerful, unknown bloodline. He didn't know if the Fourth Hokage did, but at least the Namikaze Minato of this world didn't. He had thoroughly investigated Namikaze Minato's three generations of family and indeed found no special or powerful bloodline.
Perhaps this was like the first-generation powerhouses in the early days of the Sage of Six Paths, who cultivated bloodline limits through their own talent and passed them down to their descendants—geniuses who might only appear once or twice among a large population of commoners.
In the ninja world, such individuals occasionally appear, without bloodline inheritance, relying solely on their own aptitude to gradually walk the path of the strong. Although in the realm of the Six Paths, those without a Sage's bloodline cannot become protagonists, in the realms below that, mortals still have their time to shine.
Although Fumori masaki himself wasn't very suited to learning the Rasengan, it was undoubtedly very useful for Namikaze Minato, its original creator. Therefore, he had taught him its cultivation method early on.
Unlike in the original work where he had to grope his way step by step, Namikaze Minato now had a set of experience, making learning naturally very easy. He had now completed his Rasengan training.
In the last training session, Namikaze Minato successfully carried out a surprise attack with the Rasengan, catching Fumori masaki off guard, which was equivalent to a victory.
However, Fumori masaki had now "unlocked" his abilities once again, so a normal Rasengan would likely not be as easy to use for a successful surprise attack again.
From initially only countering Flying Thunder God kunai with physical abilities, to later using Wind Release and natural energy to counter, Namikaze Minato needed to use powerful ninjutsu for a successful Flying Thunder God attack. The Rasengan was no longer as effective. Without complex tactics, the only way to win again was to unleash a move superior to the Rasengan.
That is, a semi-complete Rasengan infused with nature transformation, or a complete Rasenshuriken.