For the village elders, it could be a cause for concern as Naruto is an important figure in the village. They might try to find ways to bring him back to his normal self, perhaps by giving him new responsibilities or tasks that they hope will snap him out of his quiet state.
His enemies might see it as a sign of weakness. They could take advantage of this situation and plan an attack. Or they might be confused, as Naruto is usually so vocal and energetic, and this change in his behavior throws them off their usual perception of him.
His friends would be worried. Sakura, for instance, might try to reach out to him and get him to open up. She could be constantly checking on him, bringing him food or just sitting with him in silence, hoping he'll start talking again.
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.
It can make characters like Kakashi feel a bit annoyed. Kakashi might think Kurenai is being too overbearing and it could disrupt the normal team dynamics if he also has a role in Naruto's development.
It could make his friends worry a great deal. For example, Sasuke might be concerned about Naruto's well - being and try to reach out to him. This could lead to a new dynamic in their relationship, with Sasuke being more proactive in their friendship.
The village elders would be in a state of panic. Naruto was seen as a symbol of hope and power for the village. His departure would mean a significant loss of strength and morale. The younger generation of ninja who looked up to Naruto would also be greatly affected. They might lose their motivation and start to question the values of the village.
If Naruto has a physical disability like a broken arm that doesn't heal properly in fanfiction, his friends like Sasuke and Sakura would need to step in and help him more. Sasuke might be more protective, which could change their dynamic from a competitive one to a more collaborative one. Sakura could use her medical skills to try and find a way to heal him, which would bring them closer. His relationship with his teachers, like Kakashi, would also change as they'd have to adjust their training methods.
His friends would be hurt. They are used to the warm - hearted Naruto, and his coldness would make them feel rejected and confused. They might try to reach out to him but be constantly rebuffed.
His relationship with his sensei, like Kakashi, could become more complex. Kakashi would feel guilty for not being able to protect Naruto from the experiments. And Naruto might start to question Kakashi's ability to keep him safe. This could lead to a strain in their relationship at first, but later they could grow closer as Kakashi helps Naruto recover from the trauma of the experiments.
As for the other Konoha 11 members, they might initially be skeptical. But as they see how Sasuke is changing for the better under Naruto's adoption, they start to include him more in group activities. They come to respect Naruto's decision and see Sasuke in a new light, which gradually strengthens the overall unity among them.
Enemies would definitely be more cautious around Naruto. Those who once underestimated him would now fear his golden chakra. This could lead to some enemies trying to find weaknesses in it. Meanwhile, Naruto's new power might also attract the attention of mysterious characters who want to guide him in using it, which could cause some friction with his existing relationships as he has to decide who to trust.
His friends would be extremely worried. Sakura, for instance, would likely try to use her medical skills to help him and also try to figure out why he's doing it. She might be angry at first for him harming himself but then become very concerned. His relationship with Sasuke could also change. Sasuke might see Naruto's self - harm as a sign of weakness or, on the other hand, it could make him more empathetic towards Naruto as he has his own inner demons.