Another concept could be that Sylveon has a connection to an ancient Pokémon legend. Ash, being his curious self, gets drawn into this legend. He and Sylveon embark on a journey to uncover the truth behind the legend. Along the way, they face challenges from other trainers who also want to get to the bottom of the legend, but Ash and Sylveon's bond helps them prevail.
One idea could be that Ash discovers a Sylveon in a forest. The Sylveon is injured and Ash takes it upon himself to nurse it back to health. This could lead to a strong bond between them, and Sylveon could become a unique addition to his Pokémon team, with new adventures and battles ensuing.
Maybe in the fanfiction, Sylveon has some special powers that are different from the usual Pokémon abilities. Ash has to figure out how to work with these powers. For example, Sylveon might be able to communicate with other Pokémon in a more complex way, and Ash uses this to solve some mysteries in the Pokémon world.
Sylveon could play a crucial role in helping Ash understand the Fairy - type Pokémon better. Since Ash has experience with various types, having a Sylveon could expand his knowledge. For instance, Sylveon could show Ash how Fairy - type moves interact with other types in different ways, which would be useful in battles and strategizing.
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.
One idea could be a fanfiction where a girl joins Ash on his journey. She might have a unique Pokemon that helps Ash in a difficult battle. For example, she could have a psychic - type Pokemon that can sense the opponents' next moves and help Ash strategize better.
The beauty of Sylveon and Umbreon fanfiction is that it allows for a lot of creativity. Their different aesthetics also play a role. Sylveon's pastel colors and cute appearance can be used to create a sense of innocence in the story. Umbreon's sleek black fur and red eyes can give an air of mystery. A fanfic could be centered around a trainer who has both of them and how they interact not only with each other but also with their trainer. This can add an extra layer of depth to the story as we see their relationships from multiple perspectives.
A lot of Pokemon Sylveon and Umbreon fanfiction focuses on their friendship or a deeper connection. Some stories might show how they first met and became friends. It could be a story where Sylveon was lost and Umbreon helped it find its way back home. In other fanfics, they could be in love, which is an interesting concept considering their different types. Writers might explore how they communicate their feelings to each other. And there could be fanfictions where they face challenges together, like dealing with a powerful and evil Pokemon that threatens their home or the Pokemon community around them.
In a fanfiction about Ash's reunion in Alola, perhaps he comes back to help with an ecological problem. The Alola region's unique ecosystem is in danger, and his friends call him for his expertise. Ash brings along some of his other Pokemon from his travels, and together they work to save the day while also having a great time catching up.
Another possibility is Ash becoming Lugia. Lugia is known as the guardian of the seas. As Lugia, Ash could explore the deep oceans, discover new species of Pokemon, and safeguard the marine ecosystem. He could use his psychic and flying abilities to interact with both water - and flying - type Pokemon, bringing a new era of harmony between different Pokemon types.
In this fanfiction, Ash and May could be on separate adventures in Kalos at first. But then, they cross paths when they both get involved in a mystery related to a rare and powerful Pokémon in Kalos. They have to put their heads together, along with their Pokémon, to solve the mystery and protect the Pokémon from those who would use it for bad purposes.
One idea could be that Ash discovers a hidden power within himself related to water types. Maybe he has a special connection with a rare water - type Pokemon that helps him unlock this new ability. For example, he meets a mythical water - type Pokemon in a hidden cave. The Pokemon sees Ash's pure heart and decides to bond with him, allowing him to control water in ways he never thought possible.
In Rota, there could be a Pokemon - related prophecy. Ash and Misty are somehow at the center of it. They have to figure out what the prophecy means and how it relates to their journey. Along the way, they meet different characters in Rota who either help or hinder them. Their relationship is put to the test as they face difficult decisions based on the prophecy, but in the end, they come out stronger together.