Naruto might have a mixed reaction. He could laugh at the funny parts of the fanfiction. However, if the fanfiction misrepresents his friends or his village in a negative way, he might get angry. He's very protective of those he cares about. He may also be intrigued by the different versions of himself that are presented in the fanfiction, and might even start to think about how he can grow in those new directions.
He might be shocked at first. Just imagine seeing things that haven't happened yet. It's quite a mind - blowing experience.
Boruto might be in awe. He'd see Naruto's incredible journey filled with hardships and triumphs, and he'd probably feel a sense of pride in his father. He might also feel a bit guilty for sometimes not understanding Naruto's responsibilities as Hokage.
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.
They would be empathetic. Minato, as Naruto's father, would especially feel a deep sense of pain seeing his son struggle. He would want to reach out and comfort Naruto during his lonely times when the village shunned him because of the Nine - Tails.
Sakura might be a bit surprised at first. She would probably tease Naruto a little about it, but then she'd also be curious to see what's in those fanfics. She might even start reading some herself to see how the fans portray her relationship with Naruto.
If Naruto watches Naruto fanfiction, it would be a mind - boggling experience for him. He would see how his fans have taken the elements of his story and twisted them in different ways. He might come across fanfictions that explore his family history in more depth than the original series. Or he could find ones that pair him with characters in unexpected romantic relationships. He might even learn something new about himself from the fan interpretations, although he would also probably have to deal with a lot of out - there ideas that don't quite match his own understanding of his life.
In 'rwby watches earth fanfiction', Ruby would be wide - eyed and eager to explore every new thing. She'd be constantly asking questions about how things work. Weiss would be shocked by the lack of a Dust - based power system but would soon start to admire Earth's ingenuity. Blake would be drawn to the underground subcultures on Earth, like punk or goth cultures. Yang would be amazed by the variety of fighting styles on Earth, from martial arts to boxing. They all would have to come to terms with the fact that Earth is a very different place from Remnant.
He may laugh out loud at the funny parts. Some fanfictions are full of humorous situations and dialogues that can really tickle his funny bone.
He could be shocked at the brutality. Maybe he'll be stunned into silence at first, just taking in all the chaos and destruction.
Minati could be deeply saddened. If he has been following Naruto's journey, seeing him die would be like losing a friend. He might shed some tears and feel a sense of emptiness. He may also feel angry towards the circumstances or the character responsible for Naruto's death.