It's possible that Yahiko could be a part of the story too. Maybe through some sort of flashbacks or even if there's a way for Nagato to bring Yahiko back in a spiritual or physical form. Yahiko could influence Naruto's beliefs about peace and justice, as he had his own strong ideals that Nagato respected.
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.
Obviously Naruto and Naruko will interact a lot. But also, characters like Iruka sensei might play a role. Iruka was important in Naruto's life, and he could also be a positive influence on Naruko. And Naruto's friends like Shikamaru, Choji, and Ino might interact with Naruko as well. They could be like her aunts and uncles, teaching her different things and having fun with her.
Definitely Naruto. Then, Deidara could be an interesting character in this. His explosive personality and unique art of combat could influence Naruto in some ways. He might teach Naruto some of his skills while also getting frustrated with Naruto's different approach to things. Sasori could also be a part of it. His puppet - making skills and his cold, calculated nature could add an element of mystery to how Naruto is raised within the Akatsuki.
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.
Anko might also be involved in the story. She has her own unique relationship with Yugao and could potentially interact with Naruto. Maybe she gives Naruto some tough love or challenges him in a way that Yugao's teaching methods don't cover. And of course, Iruka sensei could also show up to check on Naruto's progress and have some interactions with both Naruto and Yugao.
Sasuke would definitely be one of the main characters to interact with Naruto. Their relationship has always been complex, and with Naruto as a girl, it could become even more so. Sakura would also interact a lot. She might be both jealous and intrigued by Naruto's new form. Kakashi too, as Naruto's mentor, would have to adjust to this change and guide 'her' in a different way perhaps.
The Raikage, Ay, would also interact with Naruto. He might be hesitant at first about Killer Bee adopting Naruto, worried about potential problems. But as Naruto shows his strength and loyalty, Ay could start to see Naruto as an asset to the village. And of course, Naruto's friends from the Hidden Leaf Village might come to visit or have some sort of communication with him, like Sakura and Shikamaru. They could be worried about Naruto living in a different village but also be proud of his new experiences.
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.
Definitely Shikamaru's friends like Choji. Naruto in Shikamaru's body would still have that bond with Choji, but it would be different. They might have conversations about food and friendship in a new light. Also, Ino would be a major character to interact with. Their relationship could change as Naruto is now in Shikamaru's body.
Obviously, Naruto and Erza would interact a great deal. Naruto would also probably interact with Erza's friends from Fairy Tail. He might meet Natsu and they could have some interesting battles or friendly competitions. He could also interact with Lucy, and perhaps learn about celestial spirits from her.
Issei would be a likely character for Evil Naruto to interact with. They could be either rivals or allies depending on the plot. Rias, as a powerful devil, would also cross paths with him. Her leadership and power would make for an interesting dynamic with Evil Naruto. And Akeno, with her mysterious nature, might also get involved in the story and interact with him in various ways.