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.
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.