It's hard to say it's extremely popular across the whole Pokemon fanfiction community. There are many different themes in Pokemon fanfiction. While the idea of Ash being betrayed in the Orre region could attract some readers who are interested in exploring darker or more complex storylines within the Pokemon world. But compared to more common themes like Ash's journey to become a Pokemon master with his regular team, it might not be as widespread.
One possible plot twist could be that the person Ash thought was his friend in Orre turns out to be working for an evil organization. Another could be that Ash's Pokemon are somehow brainwashed against him. Maybe the betrayal leads to Ash losing his ability to communicate with his Pokemon for a while.
One possible analysis could be that in such a fanfiction, the idea of Ash being betrayed might be a way to create drama. It could involve his friends or companions in the harem turning against him for various reasons like jealousy or misinformation.
Yes, in Ash Champion of Orre fanfiction, there are likely other memorable characters. There might be a local Pokémon ranger who helps Ash navigate the dangerous parts of Orre. This ranger could have a deep connection with the local Pokémon and know their secrets. A female trainer who is known for her beauty and strength could also be a part of the story. She might initially be a bit of a mystery to Ash but later becomes an important ally. And don't forget about the local Pokémon breeders who might introduce Ash to new Pokémon breeding techniques specific to Orre.
Well, in many such fanfictions, it could involve Ash being betrayed by Clair perhaps in a Pokémon battle strategy. Maybe Clair teams up with an unexpected rival against Ash, or she might break a promise regarding Pokémon training or a joint adventure.
In such a fanfiction, perhaps Ash could be betrayed by his friends in Alola. Maybe they misunderstand his actions or are influenced by some false information. For example, they might think Ash is secretly working for an enemy, which leads to the betrayal.
Well, in this kind of fanfiction, the idea of Ash being betrayed in the context of having a Mew as a mate is quite an interesting concept. It might involve a plot where Ash's friends or some other characters turn against him because of his relationship with Mew. Maybe they see it as something abnormal or dangerous.
In such a fanfiction, Ash might become extremely isolated. He could lose faith in his Pokémon and himself. Maybe he'd leave the Pokémon world in despair, feeling that all his efforts were in vain. Without the support of his friends and Pokémon, his once - strong will to be a Pokémon Master could crumble completely.
Some of the gym leaders could also be involved. Maybe they feel threatened by Ash's new - found power as a champion. They might think that Ash will change the way the Pokemon battling world works and in order to stop that, they betray him. They could spread lies about Ash misusing his Pokemon or something similar.