One possible storyline could be Sylveon and Pikachu teaming up to rescue a group of baby Pokemon from a powerful and evil trainer. Sylveon could use its ribbons to distract the trainer while Pikachu zaps the cages open.
Well, Sylveon's ability to calm others with its presence could be used in a story where Pikachu gets overly excited or scared. For example, if they are in a spooky old Pokemon mansion full of Ghost - type Pokemon. Pikachu might be too afraid to use its electric attacks effectively. Sylveon could calm it down, and then Pikachu could use its attacks more accurately. Also, Pikachu's speed with Quick Attack can be used to get Sylveon out of dangerous situations quickly, like when they are being chased by a large group of wild Pokemon. Sylveon can then use its ribbons to either hold off the pursuers or find a hiding place for them both.
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.
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.
For Pikachu, you could develop his curious side more. Maybe he's always eager to explore new areas in the fanfiction, which sometimes gets him into trouble. Sylveon could be shown as the more cautious one, using its ribbons to hold Pikachu back when he's about to rush into danger.
One idea could be that Sylveon and Pikachu go on an adventure in a magical forest together. Along the way, they discover a hidden glade filled with rare berries. As they share the berries, their friendship deepens in a really cute way.
One popular type of Pokemon Ash and Pikachu fanfiction might be adventure - based. For example, Ash and Pikachu could embark on a journey to a new and mysterious region filled with undiscovered Pokemon species. They might face challenges like difficult terrains and powerful, previously - unseen Pokemon. In this fanfiction, Pikachu's electric powers could be enhanced in some unique way, and Ash would have to strategize differently to overcome the obstacles.
One possible scenario in a fanfiction could be that Sylveon is in a happy mood and its tail wagging is a sign of its excitement. Maybe it has just found a really delicious treat or it's about to play with its trainer.
They could interact playfully, like chasing each other around in a meadow. Pikachu might zap a small bug Pokémon and Sylveon could then use its ribbons to play with it.