His teachers, like Kakashi, would likely be concerned. They've invested a lot in Naruto's training and growth. His refusal could make them question their teaching methods or whether they've misjudged Naruto's commitment. This could lead to some tense interactions as they try to understand his reasons and get him back on track.
On the other hand, some characters might support his decision. There could be those in the village who understand his need for a break or who think that the traditional training isn't the best way for Naruto. This could create new alliances or strengthen existing ones that are based on a more non - traditional view of a ninja's development.
His relationship with his teachers could also be affected. Teachers like Dumbledore, who usually encourage students to participate in such events for their growth and development, might be initially concerned or try to persuade him to change his mind. This could cause some tension between them.
It could make some relationships stronger. His friends might be in awe of his new powers and look up to him even more. But it could also create some distance, as his new status might make others feel inferior.
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 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.
His relationships could be strengthened. His friends might be in awe of his new abilities and look up to him more. They could also be a bit jealous at first, but then realize they can all grow together. For example, Sasuke might see Naruto's new powers as a challenge to overcome himself.
In terms of his relationships outside of Slytherin, like with Harry Potter and his friends, his refusal of the Dark Mark could be a step towards possible friendship or at least a mutual understanding. They might see him in a new light, as someone who is not as bad as they initially thought. However, they may also be skeptical at first, doubting the authenticity of his refusal.
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.
When Naruto snaps at Konoha in fanfiction, it has a complex impact on his relationships. With his closest friends like Sakura, she might initially be confused and try to talk some sense into him. But if Naruto is resolute, it could create a divide. His relationship with the village leaders would turn sour, as they see him as a threat to the village's stability. However, some outcast ninja in Konoha might see Naruto as a kindred spirit and side with him, which could also lead to new alliances and friendships.
The black chakra could make other characters view Naruto with suspicion. His friends might be worried that this new power is corrupting him, which could strain their relationships. For instance, Sasuke might see it as a sign that Naruto is becoming more like the enemies they've fought.