Well, it could be that Itachi trains Naruto to better control his chakra. Maybe Itachi sees potential in Naruto to bring peace to the ninja world and decides to pass on his unique skills like the Sharingan's insights on combat.
It could be Orochimaru. Since he's always after power and Naruto, with Itachi's training, would become a more appealing target. Orochimaru might see Naruto as a threat to his plans of obtaining all the jutsu in the ninja world.
For Naruto, his character growth would be significant. He's always been about friendship and protecting his loved ones. With Itachi as his trainer, he'd learn about sacrifice and the greater good from Itachi's own experiences. This would add a new layer to his beliefs. In terms of power, he'd be able to better control his chakra and develop new jutsu combinations. Sasuke would grow out of his revenge - driven mindset. Itachi's training would show him that there's more to life than just avenging his clan. He'd become more of a team player, especially when training alongside Naruto. And his skills with the Sharingan and other Uchiha abilities would reach new heights.
The plot development could be centered around Itachi's goal to change the future. He sees potential in both Naruto and Sasuke to bring about peace in the ninja world. He starts by training them separately. For Sasuke, he delves into the advanced levels of fire - style jutsu and the sharingan's true potential. With Naruto, he focuses on improving Naruto's speed and reaction time, which are crucial against fast - paced opponents like the Uchiha. As they progress, Itachi then brings them together for joint training. This forces them to learn to work as a team, something that has always been a struggle for them. Their combined skills would then be used to face threats that neither could handle alone.
One aspect of the plot could be Naruto's struggle to control the new power. The Godlike Sharingan is a powerful and potentially dangerous ability. Naruto might initially have a hard time adjusting to seeing the world through the Sharingan's perspective. Itachi would then have to guide him through this process. Also, they could face enemies who are after the power of the Godlike Sharingan that Naruto now has, leading to intense battles where Naruto has to use his new skills and the knowledge Itachi has imparted to him.
One possible plot could be that Itachi, seeing Naruto's potential and his importance for the future of the Hidden Leaf, decides to secretly train him. Itachi might teach Naruto advanced jutsu, especially those related to chakra control and unique Sharingan - inspired techniques. Naruto, under Itachi's tutelage, would grow not only in power but also in his understanding of the ninja world's complex politics and the Uchiha clan's history.
Naruto's character would develop a new sense of self - confidence. Having the Godlike Sharingan and being trained by Itachi would give him a feeling of being a part of something greater. He would no longer be just the 'loud - mouthed underdog' but a powerful ninja with unique abilities. However, he would also have to deal with the new expectations that come with this power. He might struggle with the idea of whether he is still the same Naruto or if the power has changed him too much. This internal conflict would be an important part of his character development as he tries to find a balance between his old self and the new, more powerful version of himself.
Naruto may become more calm and composed. Itachi's presence and training methods would likely instill a sense of discipline in Naruto. He'd probably be less impulsive in battles and think more before acting.
In this fanfiction, Naruto might gain some unique jutsu skills from Itachi. Itachi is extremely powerful, so he could teach Naruto advanced genjutsu or ways to better control his chakra. For example, Naruto might learn how to quickly break free from strong genjutsu attacks, which would be a great advantage in battles against tough opponents.
Well, in a fanfiction where Naruto is trained by Itachi in Sharingan, Naruto would first have to adapt to the new power. Itachi would probably start with the basics of how to activate and control the Sharingan. Since Naruto is used to his own physical and chakra - based training, this would be a challenge. However, with Itachi's guidance, he could master it. Once he does, he could use the Sharingan to analyze his opponents' fighting styles better. For example, he could quickly figure out the weaknesses in an enemy's jutsu and counter them effectively. He could also use the Sharingan's visual prowess to enhance his reaction time during battles.