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.
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.
The main characters are Ash and May, of course. Ash is a well - known Pokemon trainer with a passion for catching and training different Pokemon. May is also a trainer who has her own goals and journey in the Pokemon world. In this fanfiction, their relationship takes a turn due to the betrayal aspect.
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.
One interesting idea for the fanfiction is that May betrays Ash to protect her family. An evil group threatens her family and the only way to save them is to turn against Ash. This would create a complex situation where May is torn between her loyalty to Ash and her love for her family. Ash, on the other hand, would be completely blindsided by her sudden change in behavior.
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.
Ash could get angry. He has a strong sense of justice, and he might feel that May has violated their friendship. He could challenge her, not in a violent way, but more in a way to get an explanation and to try to make her see the error of her ways. He would likely be determined to show her that what she did was wrong.
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.
A possible fanfiction plot could be that Ash, Serena, and May are invited to a mysterious island full of unknown Pokemon. They have to work together to survive and discover the secrets of the island. Ash's leadership, Serena's ability to communicate with Pokemon, and May's quick decision - making skills would be crucial.