Sasuke would likely act like he doesn't care much. But secretly, he might be a bit intrigued as to why Naruto is into such things. He might think it's a waste of time or he could see it as another way Naruto is different from him.
Well, there are also those characters who might be a bit shocked or confused. Take Levi from Attack on Titan. He's a very serious and no - nonsense type of character. If he were to read some of the fanfic about him that deviated too much from his own self - perception, like being made into a comical or overly emotional character in the fanfic, he might be taken aback at first. But then he might also realize it's just a different interpretation and not take it too seriously.
Some Avengers might be really confused at first. For example, Tony Stark would probably be intrigued yet find it a bit odd. He'd be analyzing it like he does with new tech, trying to understand the appeal and the different universes within the anime fanfiction.
At first, Naruto might be shocked and heartbroken. He has always longed for family acceptance, so being banished by them would be a huge blow. He could feel betrayed and angry, especially if he doesn't understand the reasons behind it.
At first, Naruto may be heartbroken and confused as to why he is being bullied. He might cry in private, but in public, he tries to put on a brave face. As time goes on, he realizes that he can't let the bullies control his life. So, he tries to find friends who will support him, like Shikamaru or Choji. With their help, he begins to stand up to the bullies more effectively and also works on building his own self - confidence.
He might be initially shocked and heartbroken. Naruto has always valued his friends and the village's trust, so when that's suddenly taken away, he's in disbelief. He could try to reason with his friends at first, but when they don't listen, he might become angry and determined to prove his innocence on his own.
Naruto would be devastated. He sees Kakashi as a mentor and father figure. He might initially go into denial, not believing that Kakashi would actually abandon him.
Naruto would probably first try to fight back. He's not the type to just go along with being kidnapped. He'd likely use his Shadow Clone Jutsu to create a distraction and try to escape.