Kisame would probably be very angry at first. Samehada is his weapon and has been with him for a long time. He might feel betrayed and try to get Samehada back by force.
Iruka could be an important character. He's always been like a father figure to Naruto, and now with this new revelation, he might have to help Naruto deal with it. Hinata could also be in the story, and her feelings for Naruto could be complicated by his connection to Kisame. And then there could be some original characters created just for this fanfiction, like a ninja who was a former ally of Kisame and has some information for Naruto.
There could be. Fanfiction is a vast realm where all sorts of ideas are explored. However, I'm not sure if there is a highly popular or mainstream 'naruto is kisame apprentice' fanfiction. It might be a more niche concept, but it's entirely possible that some creative writer has delved into this idea to create an interesting story about Naruto learning from Kisame, perhaps incorporating Kisame's unique fighting style and view of the ninja world into Naruto's growth.
Well, in some fanfictions, Tobirama's character develops by learning from the mistakes of his past life. For instance, if in his past he was too strict with his rules, in his reincarnated form, he might be more lenient. He could also develop by forming new relationships that he didn't have in his previous life. Maybe he befriends someone from a lower social class in the ninja world and this broadens his perspective.
In a 'naruto and tobirama fanfiction' fight, it depends on the circumstances. If Tobirama was able to set up his water jutsu traps and strategies beforehand, he might be able to hold his own against Naruto. But overall, Naruto has shown the ability to overcome seemingly impossible odds and opponents much stronger than Tobirama. He has a wider range of abilities, from his Rasengan variations to his ability to sense and counter attacks. Tobirama would put up a good fight, but Naruto's power and experience from facing some of the toughest foes in the ninja world would probably give him the upper hand.
At first, it would be full of suspicion. Naruto is a Konoha ninja and Kisame is from the Akatsuki. But as the teaching progresses, they might develop a mutual respect. Naruto would respect Kisame's power and knowledge, and Kisame might respect Naruto's determination.
Yes, there are likely fanfictions with this concept. The Naruto fandom is vast and creative, and the idea of Naruto being Tobirama reborn is an interesting one that some fans may explore in their writing. However, the quality and availability of such fanfictions can vary greatly. You might need to search on popular fanfiction websites like FanFiction.net or Archive of Our Own to find them.
In fanfiction, anything is possible. So, Naruto could be Tobirama's reincarnation. Some fanfic authors like to play with the idea of reincarnation to bring new elements to the story. They might make Naruto inherit some of Tobirama's chakra nature or jutsu. This can create unique scenarios where Naruto has to deal with the memories or expectations that come with being Tobirama's reincarnation. It can also change the dynamics between Naruto and other characters, like Sasuke, as they might view Naruto differently if he has such a connection to an important figure from the past.
One idea could be a story where Naruto and Kisame are forced to team up during a mission that has a greater threat to the ninja world. They start off distrusting each other but gradually come to respect one another's skills.
One of Tobirama's students, like Kakashi's father, Sakumo Hatake, could be a main character. He would be eager to prove himself by finding a way to heal his teacher. He could face many challenges and grow as a character throughout the process of trying to save Tobirama.