Well, a great plot could be that they hold their wedding in a Pokemon - themed location, like a garden full of Pokemon - friendly plants. After marriage, they decide to train a new generation of Pokemon trainers. They pass on their skills and experiences, and at the same time, they also have to deal with the rivalries and jealousies of some other trainers who don't like their new - found influence in the trainer community.
One possible plot could be that Ash finally realizes his true feelings for Serena after all their adventures together. They might return to a special place from their journey, like the Kalos region. Ash would plan a simple yet heartfelt proposal, perhaps involving their Pokémon. Then the wedding could be a grand affair with all their friends from different regions coming together. Their Pokémon would also play a part, like Pikachu being the ring - bearer.
In a more elaborate plot, Ash crossdresses as Serena to infiltrate an all - female Pokemon trainer's secret society. Serena coaches him on how to act like her. As he delves deeper into this society, he uncovers a plot that threatens the entire Pokemon world. He then uses his skills and the element of surprise (since no one expects 'Serena' to be so battle - savvy) to save the day.
Perhaps in the fanfiction, Ash and Serena could stumble upon a mysterious Alola Pokémon that is said to have the power to grant wishes. They then go on an adventure to find this Pokémon, while also exploring the beautiful and diverse regions of Alola. During their journey, they help local Pokémon trainers with their problems and learn more about the Alola culture.
One idea could be Ash and Serena exploring a hidden, ancient temple in Kanto. They might discover a new, rare Pokemon species there. Another plot could involve them participating in a unique Kanto - only Pokemon tournament that has strange rules.
In a fanfiction, Ash and Serena could be invited to a royal ballroom dance in a Pokemon kingdom. There, they meet different Pokemon species that are also skilled dancers. Ash has to overcome his shyness and insecurities about dancing in such a formal setting. Serena, on the other hand, shines on the dance floor. Their dance journey in this setting could lead to Ash becoming a more confident dancer and their relationship growing deeper as they share this unique experience.
One idea could be that Ash, in Serena's body, has to participate in a Pokemon Contest. He would struggle with the grace and style required, but his battle instincts might add an interesting twist. For example, he could use his battle strategies to make his Pokemon's performance more unique. Another plot could be Serena, in Ash's body, trying to enter a Pokemon League. She might face challenges in understanding the more rough - and - tumble nature of battling compared to contests. Also, they could both have to deal with how their friends react to their changed personalities in the wrong bodies.
One idea could be Serena and Ash getting lost in a mysterious forest in the Kalos region. They have to rely on each other's skills and the Pokemon they have with them to find their way out. Along the way, they might discover a new and rare Pokemon species.
One idea could be that Ash and Serena travel back to the very beginning of Ash's journey. They could use their knowledge of future events to help Ash catch Pokémon more effectively, like getting a Pikachu right away without the initial struggle. Another plot could involve them traveling to a time when a powerful and rare Pokémon was last seen, and they have to work together to find it and protect it from evil organizations.
One idea could be that Ash and Serena are paired up for a big school project. They start off not getting along well because of their different approaches, but as they work together, they discover new things about each other and their friendship deepens. Maybe they have to research a rare Pokemon that has a connection to their town's history.
One idea could be that Ash and Dawn start a Pokemon training school together after getting married. They combine their knowledge and skills to teach new trainers. Another could be that they embark on a special journey to find a rare Pokemon as a sort of honeymoon adventure. And perhaps they have to deal with some old rivals who are a bit jealous of their relationship.