Who are the potential characters Ash could meet in 'Ash moves to Kalos fanfiction'?

Serena could be one of the main characters in the harem. She has a close relationship with Ash already in the original series. Also, Miette might be included as she showed interest in Ash. And Shauna could also be part of it as she was always friendly towards Ash during his Kalos journey.

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.

Well, it could be about Ash exploring the new region of Kalos, meeting new Pokémon and trainers. Maybe he'll participate in the Kalos Pokémon League and face some tough opponents with his Pikachu and new Kalos Pokémon he catches along the way.

Ash might meet some lone Pokémon trainers. These trainers could be on their own quests, similar to Ash's. They might have unique Pokémon or training methods that Ash can learn from.

He might meet Serena again. Since he has been to Alola and now travels to Kalos, their reunion could be an interesting plot point.

He might meet some local Sinnoh trainers who are experts in training specific types of Pokémon, like a trainer who specializes in ice - type Pokémon in the colder regions of Sinnoh.

There might be a young and inexperienced trainer who is lost. Ash, being the more experienced one, decides to help the trainer find their way. This new character could look up to Ash and in the process, Ash learns more about himself as a role model. It would be an interesting dynamic as Ash is usually the one being guided by his friends.

There could be an old wise man or woman in the Alola region who knows all about the history of the Pokémon in the area. Ash meets this person while exploring an ancient ruin. The old person tells Ash stories about the origin of certain Alola Pokémon and gives him hints on how to find rare Pokémon or evolve his existing ones in unique ways.

It could be Gary. Gary has always been a rival to Ash. Maybe in this fanfiction, Gary gets jealous of Ash's progress and decides to betray him by making false accusations to the Pokemon League about Ash using illegal training methods.

Obviously, Ash would be one of the main characters. There might also be his Pokémon like Pikachu. And he could meet new friends in Kalos like Serena, who often accompanies Ash in the official Kalos storyline.