One possible reason could be the burden of his past. Naruto has faced a lot of hardships and the memories might be overwhelming him, making him want to be alone. For example, the loss of his master Jiraiya might have left a deep scar, and he might feel that isolating himself is the only way to deal with that pain.
Maybe he feels a sense of guilt. For example, if something bad happened in the village that he blames himself for, even if it wasn't really his fault. He could exile himself as a form of self - punishment. He has always been very hard on himself when it comes to the well - being of the village and his friends.
Naruto might be hurt by fanfiction in various ways. For example, some fanfictions could distort his character. They might portray him as overly cruel or weak, which goes against his original essence in the official story. This can mislead fans who are new to the Naruto universe and create a wrong perception of him.
It could be that Anko is under some sort of mind - control in the fanfiction. And because of that, she attacks Naruto without really meaning to. Maybe she has been influenced by an enemy's genjutsu. So, she uses her powerful attacks on Naruto, and he gets hurt as a result.
Maybe she's jealous of Naruto's popularity or his strength. It's possible that she feels overshadowed by him all the time and that jealousy turns into resentment, leading her to hurt Naruto.
There are various scenarios that could play out in such a fanfiction. Maybe Naruto was injured during a mission and Kiba stumbles upon him in the forest. Kiba would then likely try to help Naruto, either by getting medical help or using his own skills if he has some knowledge of healing. This could lead to a deeper bond between them as Kiba shows his concern and Naruto is grateful for the assistance.
One possible reason could be a miscalculation in a joint mission plan. Maybe Tony and Clint had different ideas on how to approach a situation, and Tony's plan, which was ultimately followed, led to Clint being in a vulnerable position and getting hurt.
He might also use his webs to his advantage. He could try to web up Hulk's hands or feet to slow him down. Or he could create a web shield to block some of Hulk's attacks. For example, if Hulk throws a big rock at him, Spiderman could use his webs to create a net to stop the rock.
Well, while there might be some out - of - character fanfictions out there, the general perception of Naruto is that he is a very selfless character. His whole journey in the original story is about protecting others and achieving peace for everyone. So, in fanfiction, it's not very common for him to be portrayed as only caring for himself. Usually, the essence of his character is maintained, which is his altruism.
In some fanfictions, Naruto might distance himself because he discovers some dark secrets about the ninja world or his own past. These revelations could shock him so much that he needs time alone to process and figure out how to deal with them.