If Itachi's last wish is for Sasuke's safety, it could drive the plot by leading Naruto to become even more protective of Sasuke. Naruto might go to great lengths to ensure that Sasuke doesn't fall into the wrong hands or make choices that would endanger himself.
In the case where Itachi wishes for Naruto to help Sasuke understand him, it would create a strong bond between Naruto and Sasuke's journey. Naruto would constantly strive to bridge the gap between the two brothers, which could involve him facing many challenges and enemies who want to keep Sasuke in the dark about Itachi's true intentions.
Another possibility for Itachi's last wish could be the restoration of the Uchiha clan's honor. He dedicated his life to protecting the village, which led to the downfall of his clan. So, perhaps in fanfiction, he wishes for a way to reconcile the village and the remaining Uchiha members, allowing them to once again be respected within Konoha.
Itachi's teaching style, being calm and strategic, would likely have a profound impact on Naruto's growth. He might teach Naruto to be more patient and observant. For example, Itachi could show Naruto how to analyze an opponent's moves before acting impulsively, which is a big change from Naruto's usual head - first approach.
The 'last will' can also create conflicts. If multiple characters are named in a will, they might fight over the inheritance, whether it's a physical item, a property, or knowledge. This conflict can be between friends or enemies. For example, two houses in the wizarding world might battle over a powerful spellbook left in a will, which then spreads the conflict to other characters and events in the story, greatly affecting the overall plot development.
Naruto would adapt to Itachi's life in several ways. Socially, he'd have to get used to Itachi's connections and rivalries. For instance, his relationship with Kisame would be different as Naruto. He might try to influence Kisame in a more positive way. Emotionally, he'd have to deal with Itachi's internal struggles. Itachi had a lot of guilt and secrets, and Naruto would have to either come to terms with them or find a way to resolve them. And in terms of combat, he'd practice Itachi's signature moves over and over to make sure he could use them effectively in battle.
First, understand the characters well. Know Itachi's backstory, his motives, and his relationships. For example, his loyalty to the village and his love for Sasuke. Then, think about what kind of wish he might have as an adult. It could be something related to atoning for his past sins or protecting those he loves. Start with a strong opening that sets the mood and the premise of the story. Maybe start with Itachi in a moment of reflection.
It can drive the plot forward in many ways. His luck often leads to new opportunities for growth and power - ups. For example, if he finds a special item by luck, it might unlock a new ability for him, which then changes the direction of the story as he has to learn to control this new power.
It can create new challenges. For example, if Naruto can sense everything, the villains might have to come up with more elaborate ways to hide their plans or their presence, which drives the plot forward as they develop new strategies.
It can be a plot - saving device. For example, if a major character is severely injured in a battle, Naruto's healing jutsu can bring them back from the brink of death, changing the course of the story. Instead of a character dying and leading to a dark and tragic turn, they survive and contribute to future events.
Arryn's last wish could also impact the fanfic by altering the political landscape. For example, if the wish is to make Daenerys a more benevolent ruler from the start. She might not have made some of the controversial decisions she did in the original story, which would have led to different reactions from the people and other rulers.
In fanfiction, Naruto's recognition for defeating Gaara often gives him more influence. His victory can inspire other characters to train harder or change their views on certain things. It might also cause some characters to be jealous, which can create new conflicts. For instance, some ninja who thought they were stronger might feel threatened by Naruto's new - found fame and try to undermine him.