Another possibility is that it's a Pokémon in human form, which is a common trope in some fanfics. This Pokémon - turned - human could have fallen in love with Ash during their adventures together, and now they have to keep their relationship a secret from the world of Pokémon and humans alike.
Maybe it's a new character created specifically for the fanfiction. A girl from a far - off region who Ash meets during one of his journeys. She could be a powerful trainer or have some special abilities that draw Ash to her, and they start a secret relationship.
Well, it could also be about the challenges they face in keeping the relationship under wraps. Such as dealing with jealousy from other people who like Ash or his girlfriend. And there could be a plot where they almost get caught, but they manage to come up with a clever cover - up at the last minute.
It could be Misty. They have a long - standing relationship in the Pokemon series. They've traveled together and shared many adventures, so in a fanfiction, it's not a stretch to imagine her as a secret girlfriend.
It could also be a new character created specifically for the fanfic. Fanfic writers often introduce original characters to add new twists to the story. This new character could be someone who meets Ash during his travels and they gradually fall in love without the other main characters knowing.
One possible theme could be love and friendship. Since Ash has a girlfriend, the story could show how their love grows and how it also impacts their friendships with others. Another theme might be growth. Ash could grow as a person through his relationship.
Well, it could be really interesting. Maybe Ash in this fanfiction is from a well - known series, like Pokémon. His secret girlfriend could be someone he met during his travels. It might add a whole new layer of drama and romance to his adventures, changing the way we see his character.
I'm not sure which specific 'ash has a girlfriend fanfic' you're referring to. There could be many fanfics with such a premise. It might involve Ash from a particular series, like Pokémon perhaps, and the story could explore their relationship, how they met, and the adventures they have together in the fan - created world.
He might use his Pokemon adventures as a cover. Since he's always traveling to different places for battles and to catch new Pokemon, it would be easy for him to meet someone secretly. He could say he's off on a solo Pokemon - hunting trip when in fact he's meeting his girlfriend.
One challenge could be Ash's constant Pokemon journey. He is always on the move, traveling to different regions. This would make it hard to have a stable relationship as he might not be able to spend much time with his secret girlfriend.