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.
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.
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.
Yes, there are many. Some fanfictions might have him paired with Misty, creating really cute and adventurous storylines where their relationship develops over their Pokemon journeys.
Another theme is the 'reunion' theme. In fanfictions where Ash is with Serena, after being apart for a while, they meet again and reignite their connection. It often involves a lot of reminiscing and newfound feelings emerging stronger than before.
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.
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.
Well, it could be about Ash having a secret power that he's been hiding all along. Maybe it's a special connection to a legendary Pokemon that no one knows about.
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.