Perhaps a plot where Fennel is researching a particular Pokemon's behavior and Ash helps her in the field. They might encounter some problems with a group that wants to use the Pokemon for not - so - good purposes. They then have to work together to protect the Pokemon and complete Fennel's research.
For Ash, you could show his growth in understanding more complex Pokemon strategies, especially with Fennel's influence. Maybe he starts to take a more scientific approach to training, learning from Fennel's research.
Well, obviously Fennel is one of the main characters. She is often the center of the story due to her role as a researcher. Sometimes, the main character from the Pokemon games might also be a main character in the fanfiction, interacting with Fennel and helping her with her research or getting help from her in their own Pokemon journey.
Perhaps a fanfiction titled 'Ash and Fennel in the Parallel World'. In this story, they get transported to a parallel dimension where the rules of the Pokemon world are slightly different. They have to adapt quickly and find a way back home while also learning more about this strange new world and each other.
One interesting story could be about Fennel's research adventures. Maybe she discovers a new Pokemon species in a hidden area that has unique abilities. This could lead to her trying to study it while also protecting it from those who might want to use it for wrong purposes.
Begin by brainstorming ideas. You might consider how Ash and Fennel would interact in different scenarios. For example, if they were stranded on an island. What would Ash do to find food and shelter while Fennel tries to figure out how to call for help? Also, research the Pokemon world to add authenticity. Use details like different Pokemon types, moves, and abilities. This will make your fanfiction more engaging for readers who are familiar with the Pokemon universe.
There might also be a villain who wants to use the power of fennel - influenced Pokemon for their own gain. This character would add conflict to the story and be a major antagonist for the other main characters to face.
Pikachu is a very likely candidate. It's Ash's most iconic Pokemon and has a deep bond with him. Whenever Ash is in trouble, Pikachu often steps up to protect him.
Ash could be a Pokémon trainer with a different starting point in this fanfiction. Born in 1987, by 1997 he might have already made a name for himself in local Pokémon battles. He could have a team of Pokémon that he rescued from difficult situations, like a Charmander that was abandoned by its trainer. His story could revolve around giving these Pokémon a second chance and proving that Pokémon don't need to be 'perfect' to be strong.
The impact of Ash's loss in the fanfiction could extend beyond just himself. His Pokémon might also feel demoralized. However, this could also be an opportunity for them to grow stronger together. Ash could start training more intensively, seek new training methods, or even try to catch new Pokémon to strengthen his team.