Who are the main characters that could be included in a Naruto Second Hokage fanfic?

Definitely the Second Hokage. Another great addition could be the ninja who were in charge of different aspects of the village during his tenure, like the head of the ninja academy. This could show how he influenced the education and training of future generations. Also, a young and ambitious ninja from a minor clan could be a main character. This ninja could look up to the Second Hokage and strive to be like him, while also facing challenges within their own clan.

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.

The Second Hokage is a must - have main character. Additionally, some of the powerful ninja from other villages could be included. They could be the antagonists, trying to take advantage of the Hidden Leaf Village during a time of change or vulnerability. And of course, the members of his own team when he was a young ninja could be important characters, showing his growth and development as a shinobi.