It can create more conflict. His mental instability might make him unpredictable, causing his friends to be unsure how to deal with him. This could lead to internal strife within the group.
Well, if Naruto is mentally unstable in the fanfic, it could change the direction of his relationships. For instance, he might push away his friends because he's afraid of hurting them in his unstable state. This would then have a ripple effect on the overall plot as the group dynamics shift. Also, his actions due to his mental instability could attract new enemies or change the way existing enemies perceive and target him.
If Naruto becomes unstable, Sasuke might be one of the first to be affected. Since they have a deep bond, Sasuke would feel responsible to bring Naruto back to his normal state. Sakura, too, would be worried. She might try to use her medical ninjutsu skills to see if there's a physical cause for Naruto's instability and then try to find a solution.
Naruto's anger can inspire other characters. When they see how passionate he is about a certain cause due to his anger, they might be motivated to join him. For example, if he's angry about the mistreatment of a group of people, his anger can inspire his friends to fight for justice alongside him.
It can create a sense of urgency. For example, his friends and allies will then have to step up to protect him while he is unconscious. This could lead to new character developments as they face challenges without Naruto's immediate help.
His prodigy status can speed up the plot. Since he can master things quickly, he might reach high - level battles or important events faster.
It can introduce new conflicts. For example, the Uzukage might have had unresolved issues with other villages or clans, and now Naruto has to face them as the reincarnation. This can completely change the direction of the plot from the original Naruto story.
In Naruto fanfic, the size of the moon can be a plot device. If the moon is unusually large, it could attract the attention of villains who want to harness its power. This would lead to the heroes having to defend against them. On the other hand, a shrinking moon could be a sign of some dark magic at work, and the characters would need to find out the cause and stop it to save their world.
It usually makes the plot more complex. Since Naruto has the sage in him, he may need to learn to control new powers, which can lead to a series of training arcs and encounters with characters who can help or hinder his progress.
It can create a lot of internal conflict. For example, Sasuke's depression might cause him to make rash decisions that drive the plot. He could isolate himself from Naruto and the rest of the group, which then leads to the others trying to reach out to him. This pursuit can form a major part of the fanfic's plot.
It can create a lot of drama. The relationship between Hinata and Naruto was something that many fans were rooting for, so when Hinata rejects Naruto, it can shock the readers and lead to a lot of emotional turmoil in the story. This can keep the readers engaged as they wonder how Naruto will react and if there's any chance for them to get back together.
It can create a sense of growth for Naruto. Without Jiraiya by his side, he has to rely more on his own instincts and the skills he has already acquired. This can lead to new character development as he faces challenges alone.