However, Naruto also has a big heart. In the long run, he would probably try to find a way to save Kakashi or bring him back to the right side. He wouldn't give up on Kakashi easily, believing that there must be some underlying reason for his actions and that he can be redeemed.
At first, Naruto would likely be extremely shocked. He has always considered Sakura a friend and teammate, so this would be a huge blow. He might question his own judgment in trusting her.
Naruto would likely be initially shocked. He has always considered the Kyubii as a part of him and a friend in some ways. So the betrayal would be a huge blow to his sense of trust.
At first, Naruto would be completely shocked. He has always seen Hinata as a loyal friend and someone who has deep feelings for him. So the idea of her betrayal would be hard to fathom. He might try to deny it at first.
Kakashi might be initially surprised. But then, he would probably use it as a teaching moment for Naruto. He could say something like 'Naruto, stealing is not the way of a ninja.' And then give him a punishment like extra training.
One possibility could be a misunderstanding. Maybe Kakashi is framed for something that makes Naruto believe he has betrayed him. For example, an enemy could use a clone of Kakashi to perform a heinous act, and Naruto witnesses it without seeing the full picture.
Kakashi would likely be very concerned. He would immediately assess Naruto's injuries. If they were serious, he would use his medical skills to start treating him right away. His first reaction would be to make sure Naruto was stable and out of immediate danger.
Naruto could also be angry. He has always been a bit hot - headed. He might think that Kakashi doesn't trust him enough with the sword or that Kakashi is trying to undermine his progress as a ninja. So, he would likely challenge Kakashi, either verbally or by showing his determination not to give up the sword without a good reason.
Naruto might initially try to reason with those who betrayed him. He would want to understand why they did it. But if they refuse to listen or continue to be hostile, he would start to distance himself from Konoha. He could become a lone wolf, using his skills and power to survive on his own while still trying to figure out how to clear his name and get revenge if necessary. He would also likely feel a sense of betrayal towards the friends he thought he had in Konoha.
He may be surprised. Fanfictions can have some really out - there ideas that he might not have considered before. For instance, a fanfiction might have Naruto suddenly having a new, super - powerful jutsu that was never seen in the original series.
He'd probably be a mix of angry and sad. Angry at whoever or whatever caused Naruto to be in this state, and sad because he cares about Naruto so much. He might clench his fists tightly, trying to control his emotions while he focuses on helping Naruto. He'd also feel a sense of guilt, wondering if he could have prevented this from happening.