One possible scenario could be that Ash betrays May for a powerful Pokemon. Maybe he gets offered a super rare and strong Pokemon but has to cut ties with May to get it. Another could be that May betrays Ash because she is influenced by a rival trainer who convinces her that Ash is holding her back from reaching her true potential as a Pokemon trainer.
Well, in the fanfiction, it might be that Ash betrays May due to some misinformation. For example, if he hears false rumors about May working with an evil team. As for May betraying Ash, perhaps she discovers a new training method that goes against Ash's beliefs and decides to side with a group that promotes that method, thus betraying Ash in the process.
In this fanfiction, there could be a situation where Ash betrays May out of jealousy. Maybe May has achieved some great success with her Pokemon and Ash, feeling overshadowed, makes a deal with someone that goes against May's interests. On the other hand, May could betray Ash if she falls for the lies of a character who wants to use her to get to Ash. This character might make her believe that Ash has some dark secrets and that she should distance herself from him.
Perhaps in the fanfiction, there's a threat to the Pokemon world. Ash and May team up to face it. During their adventure, they rely on each other, share their hopes and fears. This mutual understanding and support lead them to a realization of their love for one another. And in the end, they plan to get married to build a future together in the Pokemon world.
It could be a rival trainer. Rival trainers are often very competitive in the Pokémon world. Maybe this rival is jealous of Ash and May's progress and decides to betray them to slow them down. They might spread false rumors about Ash and May, causing other trainers to be distrustful of them.
Perhaps a new and powerful trainer arrives in the story. This trainer manages to deceive Ash's harem members, making them think that Ash is a hindrance to their growth as trainers. As a result, they side with the new trainer and betray Ash, leaving him feeling confused and alone.
Perhaps Leaf betrays Ash because she becomes jealous of his friendship with Pikachu. She might feel like Pikachu gets all of Ash's attention and decides to side with a group that wants to separate them. This could lead to Ash having to fight not only to save Pikachu but also to win Leaf back.
One possible scenario could be that all their Pokémon friends are part of the wedding. Pikachu might be the ring - bearer, with little ribbons on its ears. Another scenario is that they have the wedding on a beach near a Pokémon Center. Ash could be wearing a traditional tuxedo, and Misty in a beautiful white dress with a water - type Pokémon motif.
In certain fanfiction stories, Ash could faint as a result of a psychological shock. Imagine if he discovers that one of his beloved Pokemon has been mind - controlled by an evil organization. The sheer horror and disbelief could be so overwhelming that he faints. Additionally, he might be caught in a powerful psychic attack from a very strong psychic - type Pokemon that not only weakens his physical state but also his mental state, leading to his fainting.
One possible scenario could be that Ash and Serena are at a Pokemon festival. The music starts and they begin to dance. Ash, who is usually more focused on Pokemon battles, is a bit clumsy at first but Serena guides him. As they dance, their Pokemon join in the fun, creating a lively and heartwarming scene.
In such a fanfiction, they might be betrayed by a so - called friend. For example, a fellow trainer could steal their Pokémon in order to gain an advantage in a big tournament. This would be a huge shock to Ash and May, and they would have to figure out how to get their Pokémon back and also deal with the sense of betrayal.
I think Ash would be angry as well as hurt. He's a passionate trainer and his friends mean a great deal to him. He might challenge May in a Pokémon battle, not to defeat her but to make her see how wrong her betrayal is. And during the battle, he would keep asking her to come back to their old friendship.
One possible plotline could be that Ash discovers May has been secretly working with a rival trainer in order to gain an advantage in a big tournament. This would make Ash feel betrayed as he thought they were friends and training partners. Another could be that May betrays Ash for a rare Pokémon that Ash was also after, choosing the Pokémon over their friendship.