There could also be Ichigo Kurosaki from 'Death'. If there is some sort of crossover event in the fanfiction, Ichigo might end up in Naruto's world. He could teach Naruto some things about fighting with a sword, which is different from Naruto's usual combat style.
Obviously Naruto himself. And from the 'Death' side, the Shinigami is very likely to show up. It's the most iconic death - related character in that universe.
Rukia Kuchiki might also appear. She could befriend Naruto and share her knowledge about the spirit world with him. And perhaps she would be amazed by Naruto's chakra and his ability to never give up, while Naruto would be intrigued by her reiatsu and shinigami powers.
Sasuke would be a likely character to appear. Since he and Naruto have a deep connection, Sasuke might cross paths with Naruto during his wanderings, either as an ally or an antagonist depending on the plot.
Iruka sensei is almost certain to be in it. He has always been important in Naruto's life. Also, Sakura might be there. She could be one of the first to welcome Naruto or perhaps she might initially be a bit cold because of her past feelings for Sasuke. Other characters like Kakashi sensei could also make an appearance, guiding Naruto in his new life in Konoha.
Obviously Naruto himself is very likely to appear. He is the main character after all. Sasuke would also be a common character as his relationship with Naruto is so central to the story. Then there are the important figures like the Hokages, especially the ones like Minato and Hashirama who had a big impact on Naruto's life. And of course, characters like Kakashi who played a major role in Naruto's growth.
Obviously, Naruto and Jiraiya would be the main characters. Naruto, the protagonist of the original series, and Jiraiya, his mentor. They have a deep connection, and any fanfiction about them meeting would revolve around their relationship.
Obviously, Naruto would be one of the main characters. He's the central figure from the Naruto universe. And then there would be the Pokegirl. She could be any type of Pokegirl, like a Pikachu - girl or a Charmander - girl. Their different personalities and abilities would drive the story forward.
The tailed beasts could potentially play a role too. Maybe they are somehow connected to the race, like being the power source for certain obstacles. And Kurama, being inside Naruto, could give him an edge in the race by providing extra chakra or unique abilities.
Well, obviously Naruto himself would be the main character. There could also be his friends like Sasuke and Sakura, who might be involved in the interactions between the two Narutos. Maybe they are confused at first by seeing two Narutos, but then they help them figure out what's going on.
Obviously, the 5th Hokage herself. Then there would probably be Naruto, as he is a central character in the Naruto universe. Sakura might also be there, as she is one of Naruto's closest friends. And Kakashi could make an appearance, given his importance in the story. Shikamaru, with his intelligence, could also be involved, perhaps as an advisor to the 5th Hokage.
Sakura would be very likely to appear. She's Naruto's friend and has always been an important part of his life in Konoha. Kakashi too, as Naruto's former sensei. He would be interested in Naruto's growth and return. His friends like Shikamaru, who is smart and has always been there for Naruto in different situations. And of course, Iruka - sensei, who was like a father figure to Naruto in the beginning. He would be overjoyed to see Naruto come back home.
Obviously, fem Naruto herself is a main character. Her father, Minato Namikaze, and her mother, Kushina Uzumaki, are the ones she is going to meet. There might also be other characters from the Naruto universe like Jiraiya, who was Minato's teacher and could potentially be involved in the story, perhaps as someone who helps facilitate the meeting.