He might be really surprised. Naruto is used to his own world and the fanfiction could show things he never imagined. For example, if the fanfiction has his kids achieving great things in new ways, he'd be proud yet a bit shocked at how creative fans can be.
He might be shocked at how the village has developed. In some fanfictions, the village could have advanced technology. Naruto, being from a more traditional ninja world, would likely be both amazed and a bit confused at first.
He might be shocked at first. In fanfiction, the future could be full of unexpected changes. He could be excited to see how his friends and the village have developed. Maybe he'd be a bit sad if things didn't turn out as he hoped for his loved ones.
Well, they may react with a bit of nervousness too. The future in the fanfic could bring new challenges like changes in the music industry trends. For example, new technologies might require them to adapt their performance and promotion methods. They might worry about whether they can keep up with the fast - paced changes while still staying true to their art. But at the same time, they would also be determined to face these challenges head - on because they have always been a group that thrives on growth and evolution.
If the future she visits is a bad one, Hermione would be determined to change it. She has a strong sense of justice and wouldn't stand by and let people suffer. She would use her knowledge of the past and her wits to find a way to make things better, whether it involves changing the actions of certain individuals or influencing the course of events on a larger scale.
The older characters such as Kakashi would be cautious. They would recognize Naruto but also be worried about the implications of someone from the future being in the present. They would want to know if his presence could change the future in a negative way. For example, they might fear that his actions could lead to the earlier awakening of a powerful enemy. As for the villains, they might see future Naruto as a threat and try to eliminate him as soon as possible. Orochimaru, for instance, would be very interested in Naruto's future powers and might try to capture him to study. And the new generation of ninja in the past would look up to future Naruto, seeing him as a symbol of what they could become.
Some of them might be shocked. Tony Stark, for instance, might immediately start thinking of ways to use technology to change what he saw. Steve Rogers would probably be more concerned about the moral implications of interfering with the future.
Some characters might be shocked. For example, Naruto himself would probably be really excited to see how his world is imagined in the future. He'd be happy to see that his story has inspired so many different ideas. Sasuke, on the other hand, might be a bit more skeptical. He'd analyze the fanfiction carefully, looking for any inaccuracies or misinterpretations of his character or the ninja world's values.
He would likely be very curious. Naruto has always been eager to learn and explore new things, so seeing future fanfiction would be like opening a door to a new world of possibilities for him.
He might be amazed at the technological advancements. In fanfiction, Howard Stark is a brilliant inventor in his own time. Seeing the future tech like advanced AI and space travel would both astonish and inspire him. He could start thinking of ways to adapt those ideas to his era, or he might feel a bit of envy for not being able to see it all in reality.