Well, Lucy would be likely to interact with Naruto. She's friendly and curious, so she'd probably be one of the first to approach Naruto and try to understand where he came from. Gray is also a candidate. His cool - headedness (pun intended) would contrast with Naruto's more energetic personality. And of course, Makarov, the guild master. He would be interested in Naruto's abilities and might offer him a place in the guild or give him some tasks to prove himself in the Fairy Tail world.
Gray would be one of the main characters to interact with Natsu. Their friendly rivalry is well - known in Fairy Tail. Makarov, as the guild master, would also have an important role in interacting with Natsu. He might give Natsu some important tasks or just have a grandfatherly chat with him about his return.
Gray is another candidate. Gray's cool and collected demeanor could contrast with Tobi's more mysterious nature. They could get into arguments about the best way to handle a situation, like when facing a powerful enemy. Or, they could find common ground in their skills and work together to protect Fairy Tail from danger.
Iron Man is another candidate. Tony Stark's technology and Naruto's ninja techniques could be a great contrast. They could learn from each other. Stark might be interested in Naruto's chakra - based powers and try to replicate them in some way, while Naruto could be amazed by Stark's high - tech gadgets.
Gray could also play a role. He is another important member of the guild. He might interact with Lisanna in various ways, perhaps in training sessions or during guild missions. His cool - headed nature could contrast with Lisanna's more warm - hearted personality, creating interesting interactions.
For Zabuza from 'Naruto' in a 'Fairy Tail' fanfiction, he would interact with the characters in a very direct and often violent way. He would see the Fairy Tail mages as targets or obstacles. If he was hired to kill someone in the guild, he would not hesitate to use his sword skills against them. He might not understand the concept of friendship and loyalty that is so strong in the Fairy Tail guild and this could lead to some interesting clashes.
Kakashi could also play a role. He has been Naruto's mentor for a long time. So, he might have some mixed feelings about Itachi adopting Naruto. He could be suspicious of Itachi's motives at first but then gradually come to understand Itachi's positive influence on Naruto. Their interactions could be really fun to read about, especially when Kakashi tries to give Itachi some advice on how to handle Naruto's wild nature.
He would likely interact with the Dragonborn. They could have an interesting exchange of skills, with Naruto showing off his Rasengan and the Dragonborn demonstrating shouts. He might also meet the various Jarls in the different holds, trying to understand their leadership styles which are different from the Hokage in Konoha.
In this fanfiction, Naruto will surely interact with his friends who might be trying to break him out or at least communicate with him from the outside. Inside the prison, he'll encounter inmates with diverse personalities. There could be a wise old prisoner who imparts some valuable wisdom to Naruto. Also, there may be a group of inmates who form a sort of gang within the prison, and Naruto has to either fight them or make peace with them depending on the situation. And of course, there could be a mysterious figure who seems to know more about Naruto's presence in the prison than he himself does, and Naruto will have to figure out this person's motives and identity.
Rukia might also interact with Naruto. She's kind - hearted and might see Naruto's potential. She could be the one to first notice Naruto's situation and try to bridge the gap between him and the rest of the Soul Society. For instance, she could introduce Naruto to some of the more open - minded Soul Reapers.
Obviously, Nagato himself would be the main character interacting with Naruto. He would be like a mentor or a guardian figure in Naruto's life.