Maybe Frilish is causing trouble in a local area, and Ash decides to catch it to restore peace. Along the way, he might learn some new strategies or form new friendships with other characters in the fanfiction world.
One possible plot could be that Ash discovers Frilish in a mysterious new region and has to overcome various obstacles like other Pokémon trainers or difficult terrains to catch it.
Well, I don't have a particular 'ash catches frilish fanfiction' at hand. However, when looking for such fanfiction, you can use relevant tags on fanfic platforms. Maybe start by searching for Pokémon - related fanfiction platforms as Ash is from Pokémon, and then narrow it down with 'frilish' in the search options. This way, you might be able to find some interesting stories.
One possible plot could be that Ash stumbles upon the shiny pokemon by pure chance while exploring a new, uncharted area. Maybe he's looking for a specific type of pokemon for a local competition and instead, he discovers this rare shiny pokemon. Another plot could involve the shiny pokemon being in danger from a group of poachers, and Ash has to rescue it. Then, after rescuing it, he forms a special bond with the shiny pokemon which is different from his bonds with his other pokemon.
One possible plot is that Latias is injured and Ash finds it. He nurses it back to health, and during this process, they form a bond. Latias then decides to join Ash's team. Another plot could be that there is a tournament where the prize is a special item that can attract Latias. Ash enters the tournament, wins, and uses the item to catch Latias.
A possible plotline could be that Fennekin is a rare and special Fennekin that only appears in a certain region. Ash hears about it and goes on a quest to find it. After a long search, he finally encounters Fennekin. Through a series of events, like helping Fennekin out of a dangerous situation, he earns Fennekin's trust and catches it.
One interesting plot could be that Ash catches a shiny Pikachu which has some unique powers, like being able to communicate telepathically with other Pokemon. This would change the way Ash interacts with his team and the challenges he faces in battles.
One possible plotline could be that Ash stumbles upon Latias while exploring a new region. Latias is initially shy but Ash's kind nature draws her in. They start to form a bond as Ash helps Latias when she gets injured by some wild Pokémon. Another could be that Latias is being chased by a group of poachers and Ash steps in to protect her. This leads to an adventure where they have to outwit the poachers and in the process, Latias decides to stay with Ash for a while.
Well, one possible interesting plot could be Ash using his unique bond with his Pokémon to outwit Mewtwo. Maybe he convinces Mewtwo that not all humans are bad through the kindness shown by his Pokémon team.
One possible plot twist could be that the legendary Pokémon start to lose their powers once caught by Ash. Another could be that there is a hidden cost or consequence to catching all of them that Ash doesn't initially realize.
One possible plotline could be that Ash meets Tapu Koko in a mysterious forest. Tapu Koko is initially cautious of Ash, but Ash shows his pure love for Pokémon through his actions like sharing his food with other Pokémon. This earns Tapu Koko's trust gradually, and eventually Ash manages to catch it in a very unique Poké Ball. It could be a special one given to him by an elder in the Alola region.
A plot could be that a lemon - loving Pokémon starts causing trouble in the area where Ash and Squirtle are. Ash and Squirtle team up to stop it, and along the way, they discover that the lemon - loving Pokémon has a sad backstory related to being over - hunted for its love of lemons. They then try to find a way to protect it and also satisfy its lemon cravings in a more sustainable way.