Obviously, Naruto would be one of the main characters as he is from the Leaf Village and would likely lead the charge against the agents of Mist. Sasuke could also be there, as he often teams up with Naruto in important battles. Sakura might be involved too, using her medical and combat skills. And from the Mist side, there could be some important ninja agents who are the antagonists, though their identities would be developed as the story progresses.
The main characters would surely include Naruto, who would be at the forefront of the Leaf's efforts. His charisma and power would be key in the war against the Mist agents. Besides him, other members of Team 7 such as Sasuke and Sakura are likely to be main characters. They have their own unique abilities that would be useful in combat. From the Mist side, we might expect to see the leaders of the agents, perhaps a ninja with a special bloodline limit or a very skilled strategist. And there could be some new characters introduced, like young ninjas from the Leaf who are inspired by Naruto and eager to prove themselves in this war.
In this fanfiction, Naruto is bound to be a central figure. He's the symbol of the Leaf Village's strength and determination. His friends like Shikamaru could also play significant roles, using his intelligence to strategize in the war. From the Mist Village, we might see some powerful and mysterious agents. There could also be some older characters from both villages getting involved, like Kakashi from the Leaf and some of the Mist's veteran ninjas. They would add depth to the story with their experience and knowledge of past conflicts.