Some would be excited. Luffy would probably be eager to jump into the future he sees in the fanfiction. He's always looking forward to adventures, and if the future seems cool, he'd be all for it.
The older characters like Rayleigh might view it as a warning or a guide. They've lived through a lot and might use the fanfiction as a way to prepare the younger characters. They could see it as a chance to prevent disasters or encourage positive development within the Straw Hat crew.
The reaction of Star Wars characters to watching the future in fanfiction would vary greatly. Consider Obi - Wan Kenobi. He would be calm and analytical, trying to understand the different paths the future could take. He might be looking for signs of the Force's influence and how he could help guide the right choices. And the stormtroopers? They might be confused at first, as they are used to following orders, but then some might start to question their roles in the future if they see a different way of life or a more just society.
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.
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.
They might be confused at first. Fanfiction can be wild and different from their real experiences.
Superman may see the similarities in the heroism of the One Piece characters to his own. However, he'd also notice the differences in how they achieve their goals. He might think about how he could incorporate some of their fearless attitudes into his own battles back home. Batman would be very observant. He'd study the motives of the villains in the One Piece fanfiction and how the heroes counter them, and might even get some new ideas for dealing with Gotham's rogues.
Obviously, Luffy would be one of the main characters. He's the captain of the Straw Hats and the central figure in the One Piece world. His actions and decisions would greatly influence any future scenarios.
They may laugh out loud if there are humorous parts in the fanfic. For instance, if the fanfic writer creates a comical situation involving the characters that is well - written.
Some characters might be excited. They could be interested in seeing how their story continues in the fanfiction. Others might be skeptical and think that the fanfiction is not a true representation of their possible futures.
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.
Luffy would be really emotional. He might laugh at the funny parts of Ace's past and cry at the sad ones. He loves his brother so much that any story about Ace would have a big impact on him.