Well, in this fanfiction, they could be on a mission to stop a new, powerful enemy that neither the Leaf Village nor Itachi alone could handle. Itachi might take Naruto to train in special places, like the old Uchiha training grounds. There, Naruto could learn new jutsu and gain a deeper understanding of the ninja world. They might also meet some of Itachi's old friends or foes, which would add more drama to their adventure.
They might go on a journey to discover the secrets of Itachi's past. Naruto could learn a lot from Itachi about the Uchiha clan and their powers. Maybe they'll encounter other powerful ninja clans along the way and have to fight or make alliances.
Naruto could have all kinds of adventures. He might get involved in a fight against one of the Earth's villains, like Frieza if he somehow showed up. Naruto's Rasengan could be a powerful weapon against such foes. He could also explore different parts of the Earth, like the mountains or the oceans, which are very different from what he's used to in his own world.
They could face off against some hidden enemies in Uzu. Maybe there are remnants of an old enemy of the Uzumaki clan who want to stop Naruto from learning about his heritage. Naruto and Kushina would then have to fight together, with Naruto learning new combat strategies from his mother.
It might be an adventure to an ancient ruin. Ash and his mom could be exploring the old, crumbling structures, looking for lost treasures. His mom might be teaching Ash about the history of the place as they search, and they could encounter some traps or puzzles along the way.
Ash could meet new friends. The city is filled with different kinds of people. Maybe he'll meet a trainer with a completely different approach to Pokémon battles, which could inspire him to improve his own skills. He might also meet locals who can show him around and introduce him to the hidden gems of Altomare.
One possible outcome is that Naruto, being in Itachi's place, might have a very different approach to dealing with the Uchiha clan situation. Naruto is known for his strong belief in redemption and friendship. He could have tried to reason with the Uchiha clan instead of the events that Itachi had to go through. This might have led to a different relationship between the Uchiha and the village.
One possible plotline could be Fem Itachi becoming Naruto's mentor. Since Itachi is highly skilled, she could pass on unique jutsu and strategic knowledge to Naruto. Another plotline might involve a romantic relationship between them, which would be a huge departure from the original story and would create a lot of drama as they navigate their feelings while dealing with the ninja world's challenges. Or perhaps Fem Itachi joins Naruto in his quest to bring peace to the ninja world, using her own methods and abilities to complement Naruto's.
In this fanfiction, Itachi might take Naruto for various reasons. Maybe he sees some potential in Naruto that he wants to cultivate away from the academy's normal teachings. It could also be part of a larger plan to protect Naruto from unseen threats in the academy environment.
Perhaps Itachi realizes that Naruto has the potential to change things for the better in the ninja world. He takes Naruto with him to train him in ways that the Leaf Village couldn't. Itachi may have some knowledge or skills that he wants to pass on to Naruto, like how to deal with the power of the Nine - Tails in a more efficient way.
They might have battles against strong Sinnoh trainers. Ash could use Charizard to take on gym leaders like Volkner. Charizard's fire - type moves would be really effective against some of the electric - type Pokémon in Sinnoh.
Well, they might go on an adventure to discover new jutsus. Sasuke could be on a mission to learn more about his clan's secrets and takes Naruto along for the ride because he knows Naruto's strength. Maybe they'll encounter powerful enemies and have to rely on each other to survive.