Perhaps it would be a combination of forces that save Ash. His own Pokémon, led by Pikachu, could start the rescue mission. Along the way, they might encounter some friendly Pokémon trainers who offer their help. And there could also be some unexpected help from a Pokémon that Mew least expects. This Pokémon could have some sort of connection to Mew and be able to convince it to let Ash go or help Ash escape while Mew is distracted.
Ash could use his Pokémon. Pikachu, for example, could use its electric attacks to short - circuit any devices or barriers holding Ash captive. His other Pokémon like Charizard could also help by using their strength or special abilities to break free.
In the 'ash is kidnapped by mew fanfiction', one possible plot is that Mew is acting out of a sense of desperation. It might believe that by kidnapping Ash, it can save the Pokémon world from a greater threat. Ash, being the protagonist, would then have to find a way to communicate with Mew and figure out what's really going on, all while trying to escape. Another idea could be that Mew is simply misinformed about Ash and thinks he's a danger, so it kidnaps him to protect the Pokémon realm.
A new villainous trainer group. They might see Ash as a threat to their plans of dominating the Pokémon world, so they kidnap him to stop him from competing in important battles or tournaments.
Many Pokémon - related forums also might have threads dedicated to sharing 'Ash Kidnapped' fanfictions. Some users post their own works or recommend stories they've read. Reddit has several Pokémon - focused subreddits where you could potentially find links or discussions about such fanfictions. Additionally, Tumblr can be a good place to look, as there are often fanfiction writers who share their works there, along with relevant tags for easy searching.
There's also a possibility that it's a misanthropic Pokémon that just doesn't like humans interfering in the Pokémon world. It sees Ash as a symbol of human intrusion and decides to kidnap him with the help of the eevee to send a message to all human trainers.
Well, perhaps Pikachu would go on a heroic quest to rescue Ash. It might team up with other Pokémon like Charizard. They could follow the kidnappers' trail, facing various challenges along the way, like battling wild Pokémon or getting through difficult terrains.
One possible plot could be that Ash is kidnapped by a rival trainer group who want to steal his Pokémon. His friends then have to embark on a rescue mission, facing various challenges and battles along the way.
There may be some popular ones that have gained a following. For example, a fanfiction where Ash is kidnapped by an ancient Pokémon spirit that has been awakened and is angry at modern Pokémon training methods. This could attract readers because it combines the familiar Pokémon world with a new and strange concept. It might also include elements of Ash having to convince the spirit to let him go through his understanding of Pokémon.
In the world of 'Ash Kidnapped' fanfictions, there are those that take a more comical approach. Maybe Ash is kidnapped by a group of Pokémon who mistake him for someone else. This could lead to all sorts of funny misunderstandings and interactions. There could also be fanfictions where Ash is kidnapped as part of a grander plot by an evil organization, and his rescue involves teaming up with unlikely allies.