I don't know for sure without reading it, but probably the trainer who is on the Alola journey, and maybe some of the well - known Alola characters like Hau or Lillie.
It could feature the main trainer as the central character. Alongside, characters like the Kahunas might play important roles. They are the leaders in the Alola region and could be mentors or sources of important quests for the protagonist. Also, any rivals that the trainer makes during their journey, perhaps someone who has a different approach to Pokemon training, could be among the main characters.
Since it's set in the Alola region, it's likely that the protagonist is the main focus. However, depending on the story, it could also have some original characters created by the fanfiction writer. These characters might be fellow trainers, or locals who help the main character in their journey. And of course, Pokemon themselves can be considered main characters in a way, as they are an integral part of the Pokemon world and the trainer's journey.
Since it's a fanfiction about Pokemon in the Alola region, it could involve the main character exploring different islands. They might take part in the island challenges, meet unique Alola Pokemon forms, and have interactions with the local characters. For example, they could team up with Hau or Lillie to battle Team Skull or discover some hidden secrets in the Alola region's beautiful landscapes.
I'm not sure specifically as it's a fanfiction, but likely it has a trainer as a main character.
I don't know for sure as it's a fanfiction. But it could be a young trainer, perhaps based on the player character in the games. Maybe there are also some unique NPCs created by the fanfiction author.
Well, it could potentially have the main character from Pokemon Red, like Red himself. He would be the one exploring the Alola region in this fanfiction.
Well, obviously Ash is one of the main characters. He's the protagonist of the Pokémon series and his journey in Alola is the focus. Pikachu is also a main character as Ash's loyal Pokémon partner. In Alola, there could be new friends like his classmates from the Pokémon school, such as Kiawe, Lillie, and Sophocles, who would also play important roles in the fanfiction.
There could be a girl named Lillie as a main character. She is shy but has a strong bond with her Pokemon. At the high school, she could be the one who is always there to help out her classmates when their Pokemon get into trouble or when they need advice on training.
One popular character could be the local Alola Pokemon Professor. He is often seen as a source of knowledge, guiding trainers in their journey in 'pokemon red alola fanfiction'.
I'm not sure specifically as there could be many different plots in this fanfiction. It might involve the adventures of the trainer in the Kalos region, encounters with new Pokemon, and the journey to become a Pokemon master.
Professor Kukui is another common character. He serves as a guide and mentor to Ash in the Alola region. He might provide Ash with new Pokémon knowledge, especially about the unique Alola Pokémon species. And of course, there are the various Pokémon trainers that Ash meets and battles in the Alola region. These trainers can range from novice trainers just starting out to more experienced ones who pose a real challenge to Ash.
Gladion is also popular. His edgy and mysterious personality can add a lot of intrigue to a story. You could write about his past, his connection to the Aether Foundation, and his journey to become a stronger trainer. Maybe in your fanfiction, he teams up with the main character for a special mission.