It could be an old, retired ninja who lives on the outskirts of the village. This person has seen the hardships Naruto faces and decides to take him under their wing.
Maybe it's a wandering shinobi who passes through the village. He senses Naruto's strong will and decides to give him some basic training before moving on with his journey.
In some versions of the fanfiction, it could be a spirit or a spectral figure. This entity is tied to the village's past and sees Naruto as the key to its future, so it starts training him in secret before the academy.
It could be an unknown ninja from a far - off village who specializes in Storm Release. This ninja might have heard of Naruto's potential and decided to train him.
In such a fanfiction, one possible plot could be Naruto training in secret. Maybe he discovers an old, hidden training ground in the village. He starts practicing basic ninja skills like shuriken throwing and tree climbing on his own. This early training could give him an edge when he finally enters the academy, making him stand out among his peers.
Maybe it's a member of a long - lost ninja clan. This clan member could have some special skills and knowledge that they want to pass on to Naruto. They choose to train him in secret to protect their clan's secrets from falling into the wrong hands.
Perhaps a fallen god who, despite losing his status, still has the knowledge of how to train a God of Destruction. This character could have his own motives for training Naruto, like regaining his former glory through Naruto's success.
Naruto might be more confident in his relationships. Since he has received training from Itachi, he would be more self - assured. He might not be as eager to prove himself in a brash way as in the original story, which could lead to better relationships with his classmates. For example, he wouldn't constantly challenge Sasuke in a show - of - strength manner.
The plot could involve Kurama teaching Naruto how to use his own chakra more efficiently. Since Kurama is a powerful source of chakra, he can guide Naruto on how to tap into his inner strength. Maybe Naruto starts to show extraordinary abilities in front of the villagers even before the academy, which causes both fear and admiration. This early training could also lead to Naruto having a different attitude towards his studies at the academy as he already has some skills.
One possible plotline could be that Itachi sees Naruto's potential even at a young age. He might start teaching Naruto basic ninja skills like stealth. For example, Itachi could show Naruto how to move quietly in the forest without making a sound. This early training could give Naruto an edge when he later enters the academy, as he would already have a foundation in some ninja arts.
It could be Kakashi. He has a lot of knowledge and skills that he could pass on to Naruto more intensively. Maybe he takes Naruto on a long - term mission where they train on the go. Kakashi could focus on improving Naruto's Sharingan - like observational skills and help him develop new strategies for combat.
Naruto would be more confident. In the original, he was often bullied and looked down upon. But with Kurama's training, he would have a sense of self - worth and power early on. He might not be as loud and boisterous, as he now has real strength to back him up.
Another option could be Itachi. Although Itachi is from a different village and has his own complex situation, in a fanfiction scenario, he could secretly train Naruto. Itachi has extremely powerful jutsus and a deep understanding of the Sharingan. Training under him would give Naruto a very different perspective on power and combat, not to mention some insights into the Uchiha clan.