Well, it would likely include Naruto himself as he is central to the Naruto universe. Since it's about the Hidden Hokage, he would probably be a main focus.
Obviously, Naruto would be one of the main characters as it's about him becoming the sixth Hokage.
I'm not entirely sure without reading the fanfic, but it could be Naruto and his friends like Sasuke and Sakura. Since Naruto is aiming for the Hokage position, his friends might play important roles in the story, either supporting him or having their own arcs related to the perks of the Hokage.
Obviously, the new Hokage would be one of the main characters. It could be a character we already know like Naruto's son, who has inherited his father's determination and strength.
Since I haven't read it, I can't say for sure. But it might include Naruto and some of his friends as they are central to the Naruto universe. And of course, the character who is proposed as the'real' fifth Hokage.
In these fanfics, Kakashi could be a popular character. He was Naruto's teacher and now he could be an advisor to Naruto as Hokage. His wisdom and experience would be invaluable. And of course, characters like Shikamaru, who is known for his intelligence, could also be important in helping Naruto govern the village.
Sasuke is also frequently featured. His relationship with Naruto, whether it's as a rival or a partner in protecting the village, adds a lot of depth to the stories. In some fanfictions, Sasuke might play a crucial role in helping Naruto deal with threats to the village from the shadows.
Well, Naruto himself might still be a main character, but in a different role. Maybe he's being trained in intelligence - gathering rather than just combat.
Obviously, the Second Hokage himself should be a main character. His brother, the First Hokage, could also be included, perhaps in flashbacks. Then there could be some of his students, like Hiruzen Sarutobi. The Uchiha clan members might be important characters too, since they play a significant role in the village's history and the Second Hokage had interactions with them.
Sasuke could also be a candidate in some fanfics. He has his own set of powerful abilities and a complex personality. A story could be written where he decides to take on the role of Hokage at a young age to bring about change in the village in his own way, perhaps using his Sharingan and new techniques he develops.
In addition to the main characters like Naruto, including the new generation of shinobi such as Boruto, Sarada, and Mitsuki would be great. They represent the future of Konoha and can have their own storylines within the fanfic. Shikamaru, as Naruto's advisor, is also a must - include character. His intelligence and strategic thinking can add a lot to the story.