Well, they might feel a range of emotions. Some could be angry, feeling that they were wronged after putting their trust in Ash. Others might be heartbroken, especially if they had deeper feelings for him. For example, one of the harem members who was really close to Ash might go into a state of denial at first, not wanting to believe that he could do such a thing.
A common theme in such fanfictions could be Ash's adventures in Alola while building relationships with different characters. Maybe he forms special bonds with his Pokémon and the people around him in a more romantic or friendship - deepening way.
Often, they start with Ash having some kind of encounter with each character. For example, he might save a girl from a wild Pokemon, which starts their connection. Then, as they travel together, their relationships grow. They might share moments of training Pokemon together, or having deep conversations around the campfire at night.
One common theme is friendship. Despite the harem aspect, the relationships often start from a place of friendship. For example, Ash might be friends with different characters first and then the harem - like situation develops.
I'm not entirely sure specifically as 'ash harem lemon fanfic' could be about a lot of things. But generally, if it's a fanfic about Ash, it might be about his adventures with a harem of characters in a fictional world created by the fanfic writer. However, without reading it, it's hard to be more precise.
A common theme is adventure. Since Ash is often associated with traveling and exploring, in harem fanfictions, his harem members usually accompany him on these adventures. For example, they might go on a journey to find rare Pokémon together.
Pokemon Ash x Harem Fanfiction often plays with the idea of alternative storylines. Ash's journey in the official Pokemon series mainly focuses on his goal of becoming a Pokemon Master. However, in these fanfictions, the harem aspect adds a new dimension. It can lead to different types of adventures that are not just centered around Pokemon battles. For instance, there could be a story where Ash has to protect his female friends from a new kind of threat in the Pokemon world, which forces him to use his skills in different ways. Moreover, the interactions between Ash and the characters in his harem can show different sides of his character, like his loyalty and protectiveness.
One possible analysis could be that in such a fanfiction, the idea of Ash being betrayed might be a way to create drama. It could involve his friends or companions in the harem turning against him for various reasons like jealousy or misinformation.
One reason could be power. Maybe he was offered a great deal of power by an outside force in exchange for betraying the harem. Another could be jealousy. If there was someone in the harem who was getting more attention or was more successful than him in some way, he might have been driven by envy to betray them.
Often, in 'pokemon ash and harem fanfic', Ash becomes more confident. With the support of the characters in his harem, he might take on tougher challenges. For example, if a girl in the harem is really good at a certain type of Pokémon battle, Ash could learn from her and become better at that too.