One possible non - sexual fanfiction could be about Ash and his adventures with all the Eevee evolutions. They could be on a journey to save a special Eevee from an evil team. Ash would use his skills and the unique abilities of each Eevee evolution like Vaporeon's water powers to cross rivers, Jolteon's electricity to power up old machines, and Flareon's heat to keep them warm in cold areas.
Some fanfics might have Eevee evolving into a form that combines two existing evolutions, like a mix of Jolteon and Flareon. This could be due to some strange scientific experiment in the fanfic's plot.
Fanfiction writers sometimes give Ash's Pokemon mega evolutions that are related to the environment or a specific location. For example, if Ash is in a snowy area, his Snorunt could mega evolve into a form that is better adapted to the cold. It could have ice - based attacks that are more effective in the frigid climate, and its body might be covered in a thicker layer of ice for protection. This kind of portrayal adds an interesting layer to the story and the battles that Ash participates in.
A family - friendly fanfiction might have Ash and the Eevee evolutions teaming up to solve a mystery in a forest. They might discover an ancient Pokémon relic. The Eevee evolutions like Vaporeon could use its fins to dig in the water near the relic site, and Jolteon could use its speed to quickly search the surrounding areas for clues.
The change in its appearance can make it scary. For example, if its usually cute yellow fur turns dark or if its bright red cheeks become a sinister red glow. Also, if it starts to behave in an uncharacteristic way, like making menacing noises instead of its usual cute sounds.
Obviously, the main characters are usually Pikachu. But sometimes, there could be other Pokémon that play important supporting roles. For instance, a Pichu could be a sidekick or a younger Pokémon that the Pikachus are protecting.
One interesting plot could be two Pikachus from different regions meeting and learning about each other's unique electric attacks. For example, one Pikachu might know a special move that the other has never seen before. They could then teach each other and become stronger together.
One idea could be a story where a female Eevee evolves into Sylveon in a lemon grove. The sweet scent of the lemons could have some sort of magical influence on her evolution. Maybe it gives her powers related to the freshness and energy of the lemons, like the ability to heal others with a touch that smells like lemon blossoms.
Naruto would probably be really excited. He'd treat Pikachu like a new friend and teammate. He might try to learn all about Pikachu's powers and how it can help in battles. For example, he'd be eager to see Pikachu use Thunderbolt in a fight against an enemy ninja.