Well, Naruto himself might be really focused on Pain's motives in the fanfiction fight. Since he always tries to understand his opponents. Sasuke could be analyzing Pain's jutsu and thinking about how it compares to his own power. And Sakura might be worried about the destruction caused, just like she was in the original story when Pain attacked the village.
The characters would have a mix of reactions. For example, Kakashi would be observing every move Pain makes in the fanfiction fight very carefully, as he is a strategic thinker. Shikamaru would likely be trying to figure out the best way to counter Pain's attacks in that fictional situation. And Hinata might be feeling empathetic towards Pain if the fanfiction delved into his backstory, while still being concerned for the safety of the village and her friends.
Some characters might be amused. For example, Naruto himself could find it funny to see how others imagine his adventures in different ways. He might laugh at some of the out - of - character interpretations but also be intrigued by the creative storylines.
Ruby would be the most enthusiastic among RWBY characters. Since she is always eager for new and exciting tales, the Naruto fanfiction would be like a new world for her to explore. Weiss, being the more refined one, would look for the literary merits in the fanfiction. Blake, with her own complex backstory, would resonate with the character - driven plots in Naruto fanfiction. Yang, on the other hand, would just want to see some epic showdowns and would get pumped up during those parts.
Sakura would be interested in how the fanfiction depicts her growth and her relationships, especially with Naruto and Sasuke. She might be flattered if she is shown as a strong and important character in the fanfiction. On the other hand, she could be a bit annoyed if the fanfiction undermines her abilities or portrays her in a negative light that she doesn't deserve.
They might be really intrigued. Ruby, with her love for adventure stories, could be excited by the unique jutsus and battles in Naruto fanfiction. Weiss might be a bit critical at first, but then get drawn into the complex relationships. Blake could find parallels between the themes of discrimination in Naruto and her own experiences in RWBY.
They might be really confused at first. Naruto characters come from a very different universe with its own set of rules like chakra and ninja clans. RWBY has things like semblances and Dust. They'd probably be intrigued by the unique world - building in RWBY fanfiction.
He might be really surprised. He could find it strange to see different versions of his own story and the people around him in the fanfiction.
He might be really amazed. He'd see different versions of his world and himself, which could make him think about his own life and choices in a whole new light.
Naruto might feel a bit of nostalgia. He would see elements of his own past and how the new generation, like Boruto, is being portrayed in these fictional stories. He could also be proud to see how much his son has inspired fans to write so many different stories.
In the fanfiction, Bardock might be in a state of awe. Goku's fight against Buu is no small feat. Bardock would likely note Goku's ability to keep getting back up, no matter how hard Buu hits him. He might also be thinking about the power levels involved. In his time, the power levels he knew were much lower. Now, seeing Goku take on a foe as powerful as Buu, he'd realize just how much the Saiyan race has evolved, especially with Goku as a prime example.
They might be quite surprised. Some characters could find it strange to see their own stories being reimagined in different ways by fans. For example, if Sherlock Holmes were to watch elementary fanfiction, he might be intrigued by the new interpretations of his deductive reasoning skills or his relationships with other characters like Watson.