It could be that Mew has some sort of special power or knowledge that certain groups in the Pokémon world are after. They see Ash as an obstacle to getting what they want from Mew. So, they scheme to make everyone think Ash is untrustworthy. His friends, not knowing the truth, end up betraying him. Ash then has to fight against all odds to protect Mew and regain the trust of his friends.
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.
Well, in such a fanfiction, it might be about Ash being betrayed while somehow involved with Mew. Maybe his friends turn against him in the story for some reason related to Mew, like perhaps they suspect him of misusing Mew's power or something similar.
One possible main plot could be that Ash hears rumors about a Mew sighting in a far - off, unexplored region. So, he decides to embark on a journey to find it. Along the way, he meets new friends and foes, all while being driven by his desire to meet Mew.
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 plot could be that within the fanfiction world, there is a new character introduced who seems to be a great ally at first. This character gains the trust of Ash and Brock over time. However, this new character has a hidden agenda. They might be from a rival region and their goal is to undermine Ash and Brock's reputation in the Pokemon world. So they start spreading false rumors about them and turn other trainers against them, thus betraying their new - found friendship.
Well, perhaps Clemont betrays Ash because he becomes envious of Ash's success. Maybe he gets influenced by some dark force in the Pokemon world that convinces him to steal Ash's Pokemon or to lead him into a dangerous trap.
The main character is surely Ash. He is the one who is being betrayed. Mew is another important one. It might be that Mew is the cause, directly or indirectly, of Ash's betrayal. Then, Ash's Pokémon partners are likely to be main characters too. They might be confused or forced to side against Ash. And there could be some antagonists in the story, perhaps some evil trainers or organizations who are behind the plot to make Ash look bad and get betrayed.
Perhaps in this fanfiction, Ash discovers that he has a deeper connection to Mew than he ever thought. It could involve Mew choosing Ash as a special trainer to carry out a very important mission in the Pokémon world, such as saving a certain region from a new and powerful threat. This would lead Ash to face many challenges and grow in ways he hasn't before.
In such a fanfiction, the plot could involve Ash being betrayed by his long - time friends. Maybe they envy his success in the Pokemon world. For example, Gary could spread false rumors about Ash in the new region, causing the local trainers to distrust Ash. This would make Ash's journey in the new region much more difficult as he has to not only deal with new Pokemon and challenges but also regain his reputation.
It could be that Lillie betrays Ash because she believes it's the only way to achieve a greater good in the Pokémon world. She might think that Ash's methods are too dangerous or not in line with what she believes is right for the future of Pokémon and humans alike. This would create a complex conflict between their ideologies.