Another reason could be that he witnesses corruption or unfairness within the village leadership. If he sees that the system is rigged against certain groups, including himself or his friends, he could grow to hate Konoha and decide to leave.
This type of fanfiction concept is really out of the ordinary. Naruto's character is built on his values of friendship, loyalty, and his dream of becoming Hokage. Killing Sasuke would mean betraying all of that. However, in a fanfiction, the author might be exploring the 'what - if' scenario. For example, what if Sasuke's actions against Konoha were so heinous that Naruto felt he had no choice? But still, it's a far - fetched and very different view from the original Naruto we know.
Sasuke might be more understanding. Given his own experiences of leaving Konoha, he could respect Naruto's decision. However, he might also secretly plan to keep an eye on Naruto from afar to make sure he is safe.
It could create a sense of unease and fear. Naruto is a very powerful ninja, and if he turns dark and leaves, the villagers would be worried about him coming back as an enemy. It might also lead to a decrease in morale among the ninjas who once considered Naruto a friend or ally.
Well, perhaps Naruto is neglected in Konoha because of his past or the way he behaves. He leaves and stumbles upon a hidden village that has different values. There, he is welcomed and trained further. As he grows stronger, Konoha realizes their mistake. Naruto has to decide whether to forgive Konoha and return or stay in his new - found home where he is respected.
Perhaps Naruto leaves because he wants his child to grow up away from the pressures and expectations that come with being in Konoha. He might feel that the outside world can offer a more peaceful and normal upbringing for his family.
Naruto might meet another lost ninja. This ninja could be from a destroyed village. They would understand each other's pain and loneliness. Together, they decide to start a family, building a new life far away from the memories of their past tragedies.
One possible reason could be that Naruto discovers some dark secrets about Konoha that shatter his idealized view of the village. Maybe he finds out that the village elders were involved in unethical practices, like using shinobi for immoral experiments. This would make him lose faith in Konoha and decide to leave.
In this fanfiction, Naruto might find a peaceful place outside Konoha to build his home. He could meet someone special, perhaps a kind - hearted traveler. They would fall in love and start a family. Their days could be filled with simple joys like farming and fishing, away from the chaos of ninja battles.