I'm not sure specifically as there could be many different takes in fanfiction. It might involve scenarios where Ash and Lillie break someone's trust, perhaps in the context of their adventures or relationships within the fan - created story.
I'm not aware of any particularly popular ones off - hand. Fanfiction is a vast world, and while there might be some great 'ash and lillie betrayed' stories out there, it's hard to single out popular ones without doing a more in - depth search.
Ash would be extremely hurt. He's a very loyal person, and having someone he cares about like Lillie betray him would be a huge blow. He might initially go into denial, not believing that Lillie could do such a thing.
It could be that Lillie betrays Ash because she believes it's the only way to achieve a greater good in the Pokémon world. She might think that Ash's methods are too dangerous or not in line with what she believes is right for the future of Pokémon and humans alike. This would create a complex conflict between their ideologies.
One popular 'Betrayed Ash x Lillie fanfic' is 'Ash's Betrayal and Redemption with Lillie'. It delves deep into the relationship between Ash and Lillie after Ash has been betrayed by his so - called friends. The story shows how Lillie stands by Ash and helps him regain his confidence and strength. It has great character development and an engaging plot.
The contrast in their characters. Ash is usually a determined and brave trainer, but when betrayed, he becomes vulnerable. Lillie, on the other hand, is often seen as gentle and kind. When she steps in to support Ash, it creates a really interesting dynamic. It's like the classic 'damsel in distress' role reversed, which makes the fanfic appealing.
One characteristic is the focus on their relationship. It could be a friendship or something more. Another is the use of the Pokémon world as a backdrop. For example, they might go on Pokémon - related adventures together. Also, it often shows their growth as individuals. Like Lillie becoming more confident or Ash learning new battle strategies.
In fanfiction, the idea of Ash and Lillie having a baby can be really interesting. It often explores their relationship in a new way. Maybe it shows how they grow as a couple and deal with the responsibilities of raising a child. This could bring out different sides of their personalities.
One great 'Ash and Lillie date' fanfiction is 'A Day in Alola' which beautifully depicts their day out exploring the unique places in Alola. They visit the beach, share some local treats and have really cute interactions.
One great Ash and Lillie fanfiction is 'A Journey Together'. It beautifully depicts their adventures in the Pokémon world, showing how they support each other. Another is 'Ash and Lillie's Bond', which focuses on the deepening of their relationship as they face various challenges. There's also 'Lillie's Growth with Ash' that details Lillie's development as she travels alongside Ash.