One reason could be that he's tricked or lured away. Maybe there's a villain in the fanfic who convinces Naruto that he'll find true friends or power outside of Konoha. Naruto, being young and naive, falls for it and leaves.
In some fanfics, Naruto might leave Konoha as a child because he feels ostracized. Since he's the jinchuriki of the Nine - Tails, many villagers fear and shun him. He could get tired of the constant cold shoulders and decide to leave in search of a place where he'll be accepted.
Another possibility is that Naruto accidentally discovers some dark secret about Konoha. It could be something related to how the village treats jinchurikis or some other unethical practices. Horrified by this discovery, he decides to leave Konoha at a young age.
Perhaps he is lured away by an unknown force. In some fanfictions, there might be a mysterious character or group that tricks Naruto into leaving Konoha. They could make false promises about his parents or his true power, making him curious enough to follow them.
One possible reason could be for Naruto's safety. Maybe she has to go on a dangerous mission and believes Konoha is the safest place for him. Another reason might be that she is forced by some powerful enemies who threaten Naruto's life if she doesn't leave him in Konoha.
One reason could be to protect Konoha from a great danger that he can only face by leaving. Maybe there's a powerful enemy who has a vendetta against Naruto but would spare Konoha if he goes far away. Another reason might be a sense of self - exile due to some event that made him feel he no longer belongs in Konoha, like a misunderstanding where the villagers turn against him again.
One possible reason could be for his safety. Konoha is a well - protected village with many skilled ninja. She might believe that leaving him there would ensure he has the best chance at survival and growth as a ninja. Also, she may have some mission or obligation that forces her to leave him behind, perhaps something related to the greater good of the village or the ninja world in general.
One possible reason could be a sense of disillusionment. Maybe Naruto discovers some dark secrets within Konoha's leadership that make him question his loyalty. For example, if he finds out that some decisions were made that put the village at risk for the wrong reasons.
Yes, there might be such fanfics. One possible reason could be exploring alternative storylines. Writers might want to break the traditional view of Naruto's loyalty to Konoha to create more complex and unique plot twists. For example, they could be imagining a scenario where Naruto discovers some dark secrets about Konoha that make him question his loyalty.
Another possibility is that he wants to explore the world outside Konoha on his own terms. Naruto has always been curious, and in a fanfic, he might decide that he can't be tied down to one place. He could be on a quest for self - discovery, believing that Konoha's environment is limiting his growth.
Maybe there are some dark secrets within Konoha that he discovers in the fanfic. These secrets could be related to the treatment of certain individuals or something more sinister about the village's leadership. Discovering such things could make Naruto decide to leave in order to distance himself from the corruption or unfairness.
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.
One reason could be to gain more power. In many fanfictions, Naruto realizes that the threats he faces are far greater than what he can handle with his current skills in Konoha. So, he decides to leave and train in a more secluded and challenging place to enhance his abilities.