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.
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.
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.
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.
Well, in some fanfictions, Naruto might defeat Kisame in a battle and take the sword as a trophy. Maybe he uses his newfound Sage Mode powers or some other advanced jutsu to overpower Kisame and claim the sword.
In a fanfic of Kisame and Itachi taking Naruto, it might explore the relationship between the two Akatsuki members and Naruto. Itachi has his own complex reasons for his actions, and Kisame is his loyal partner. When they take Naruto, Itachi might be conflicted as he has a connection to Naruto through Sasuke. They could end up in a situation where they have to make a choice about what to do with Naruto.
In some fanfics, Itachi and Kisame might save Naruto because they realize his potential importance to the overall balance in the ninja world. Itachi, having his own hidden motives and a sense of protecting the village from afar, could see Naruto as a key figure. Kisame, following Itachi's lead, would also be involved. They might save Naruto from a group of rogue ninjas who are after Naruto's power. This would create an interesting dynamic as Naruto would be both suspicious and grateful towards them.
In the fanfiction, it could be that Kisame gives Naruto Samehada as part of a deal. Maybe Naruto has to do something for Kisame in return. Naruto might struggle with the idea of making a deal with an Akatsuki member but decides it's worth it for the power of Samehada. Once he has it, he might face opposition from his friends and village elders who are suspicious of his new weapon and the way he obtained it.
One popular fanfic could be 'The Encounter' where Itachi and Kisame are on a mission to find Naruto. In this fanfic, they face various challenges while tracking him down. It shows their unique abilities as they navigate through different terrains in the Naruto world. They might encounter other characters along the way who either help or hinder their search.