Mallow is another great choice. With her love for cooking and Pokémon, she could use her skills to create special Pokémon food for Ash's team. This could lead to some fun and heartwarming moments between them, and also bring the whole harem together as they enjoy the food.
One possible main character could be Misty. She could be a student at Harem High School who has a long - standing friendship with Ash. Her feisty and determined personality would add a lot of drama and interaction to the story. She might be jealous of the attention Ash gets from other students, creating some interesting relationship dynamics.
Lillie is really interesting. She starts off as a shy girl but grows a lot in her confidence when it comes to Pokemon. Her relationship with her family and their connection to the Aether Foundation adds depth to her character. Then there's Kiawe, who is very proud of his Alola heritage and his strong fire - type Pokemon. His no - nonsense attitude and his eagerness to prove himself make him stand out. And Sophocles, the tech - savvy kid, is always coming up with cool gadgets to help in Pokemon battles or exploration, which is super fun.
Brock could also be a main character. Since he has knowledge about Pokémon care and breeding, he could be Ash's colleague in the fanfiction. They could work together on projects related to Pokémon health and nutrition.
Latios would obviously be a key character. Also, Pikachu, Ash's loyal Pokémon partner, would be there. Maybe Misty or Brock could also be part of the story, with them either supporting or being skeptical of Ash's newfound admiration for Latios.
A young girl named Mia might be a character too. She is also a Glacion fan and is very competitive. She challenges Ash to various Glacion - related challenges, like a Glacion knowledge quiz or a race to find a hidden Glacion item in the forest.
May could be one of the main characters. She could join Ash on his journey and share her knowledge about Hoenn's Pokemon with him. Another could be Brock, still tagging along to offer his expertise in Pokemon care.
Well, Pikachu could still be a main character. Even if Ash hates everyone, Pikachu might be the one trying to bring back the old Ash. Maybe Team Rocket could also be main characters. They are always around Ash, and his new - found hatred could make their interactions even more interesting. They might be confused by his change or even try to take advantage of it.
A common theme in such fanfictions could be Ash's adventures in Alola while building relationships with different characters. Maybe he forms special bonds with his Pokémon and the people around him in a more romantic or friendship - deepening way.
Lillie is a likely character. She could befriend Ash and they might go on Pokémon adventures together. She has her own story and growth in the Alola region, and interacting with Ash could add more depth to both of their characters. Also, Ash might meet the Trial Captains like Mallow or Sophocles. They could challenge Ash in different ways and teach him about the island challenges.
His best friend from before the war could be a main character. This friend might have been waiting for Ash's return and now has to deal with the changed Ash.