The main character could be a young trainer who just transferred to the Pokemon high school. He or she might be shy at first but has a really strong bond with their starter Pokemon, like a Pikachu. This character would grow throughout the story, making new friends and facing various challenges related to Pokemon training and school life.
It could be a group of friends. For example, there could be a girl who specializes in water - type Pokemon like Squirtle, a boy who has a passion for fire - type Pokemon such as Charmander, and another student who is really into grass - type Pokemon like Bulbasaur. They are all in different grades at the Pokemon high school but get involved in an adventure together that tests their friendship and Pokemon - training skills.
The main character could be Ash's son or daughter. They inherit Ash's love for pokemon and enroll in the high school. There could be a group of female classmates like Misty's niece and Brock's sister who form the harem around the main character, each with their own unique pokemon and personalities.
The main character could be a young trainer named Ash. He's always eager to learn more about Pokemon and is very friendly. Another character could be Misty, a girl who is really good with water - type Pokemon and is a bit of a tomboy. There could also be Brock, who is knowledgeable about Pokemon care and often gives advice to other students.
Gary could be a main antagonist. He might be jealous of Ash's popularity at school and constantly try to undermine him in Pokemon battles and in front of their classmates.
Obviously, Ash is one of the main characters. He is the central figure around whom the story revolves. Then there are the members of his harem, though without knowing the specific fanfic, it's hard to name them exactly. But usually, they would be characters who have a special connection with Ash, whether it's through Pokemon battles, shared interests in Pokemon research, or just being good friends.
The main characters are obviously May and Drew. May is often known for her determination in Pokemon training and contests. Drew, on the other hand, is a skilled trainer with his own unique style.
I think it could be a group of friends including Brock. In high school, Brock could be the love guru for his friends, while he also has his own love interests. And among the group, there could be a couple like a female trainer with a Jigglypuff and a male trainer with a Psyduck. Their Pokémon's cute and clumsy natures add to the charm of their love story as they navigate high school life together.
The main character could be a young trainer named Ash. He's always full of energy and has a Pikachu by his side. His best friend, Gary, could also be a main character. Gary is a bit of a rival but also a great friend. And then there could be Misty, a strong - willed girl who has a love for water - type Pokemon. They could all get into various adventures at the high school.
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.
I'm not entirely sure without reading it specifically, but usually in a high school fanfic like this, there would be two main characters. They could be students with different personalities, like one might be really outgoing and the other more shy.