The main appeal is their relationship. In the series, they have a special bond. Fanfictions allow fans to explore this bond further, whether it's romantically or as great friends. It gives a chance to see them in new situations not shown in the original series.
One great fanfiction could be 'Ash and Serena's Unseen Adventure'. It might explore their relationship further as they journey through a new region filled with unique Pokemon. Another could be 'Serena's Dream Come True with Ash', where Serena finally achieves her long - held dreams while Ash is right by her side supporting her. And there's also 'The Bond of Ash and Serena', which delves deep into how their bond grew over their adventures.
In fanfiction, if Ash were to die in Pokemon XYZ, it would be a huge shock to the Pokemon world. His friends like Pikachu would be devastated. Maybe Team Rocket would even feel a strange sense of loss. It could lead to a whole new storyline where his friends try to avenge his death or carry on his legacy of becoming a Pokemon Master.
He could die in a battle against a very powerful and evil Pokemon. Maybe a new, extremely strong legendary Pokemon that he underestimated, and it managed to land a fatal blow.
In many Pokemon fanfictions, Ash might comfort Serena by simply being there for her. For example, if Serena is feeling down about a failed performance in a Pokemon Contest, Ash could offer words of encouragement like 'You'll do better next time, Serena. I've seen how hard you practice.' He might also share his own experiences of facing setbacks in Pokemon battles to make her feel that she's not alone in facing difficulties.
One possible reason could be a miscommunication. Maybe Serena did something that Ash misinterpreted. For example, she might have made a decision about their pokemon journey without consulting him, and Ash, being independent, took it the wrong way.
Obviously, Dark Ash is one of the main characters. He's the center of the story with his transformed state. Serena might also be a main character as she could be trying to reach out to Ash or deal with the new Dark Ash.
A possible fanfiction plot could be that Ash, Serena, and May are invited to a mysterious island full of unknown Pokemon. They have to work together to survive and discover the secrets of the island. Ash's leadership, Serena's ability to communicate with Pokemon, and May's quick decision - making skills would be crucial.
The writing style matters a lot. A great Pokemon XYZ Ash x Reader fanfic uses vivid descriptions to bring the story to life. It makes you feel like you are right there with Ash and the reader. The dialogue should be natural, as if it could actually be something Ash would say in the series. Also, the fanfic should have some emotional depth, whether it's the excitement of a new discovery or the warmth of the relationship between Ash and the reader.
One possible interesting plotline could be Dark Ash's struggle with his new, darker side while still having memories of his former self. Maybe he has to face off against his old friends who don't recognize him at first.