His Pokémon, like Pikachu, would surely be important characters. Pikachu might be the first to suspect that Ash is not really dead and start searching for him. Misty and Brock could also be main characters. They are Ash's long - time friends and would be deeply affected by his supposed death. They might be the ones to uncover the truth behind his faked death and help him in his plan, or they could be completely in the dark at first and then gradually figure things out.
Definitely Pikachu. It has such a strong bond with Ash. Then there could be Serena. She might play a big role as she has feelings for Ash. She could be heartbroken at first by the news of his death and then become determined to find out the truth. Another character could be Gary. He has a long - standing rivalry with Ash, but deep down he respects him. He might initially be skeptical about Ash's death and start his own investigation, which could lead to some interesting interactions and plot developments.
Obviously, the Legendary Pokemon would be a main character. It could be a Pokemon like Mewtwo, who is often depicted as having a complex personality. It might start off as a mysterious and powerful entity that Ash has to befriend or battle against.
There could be a new character, a rival to Ash's dad from his younger days when he was an active Pokemon trainer. This rival could reappear in the fanfiction, causing some trouble or adding some drama to the story.
There could be Brock. He might play an important role in guiding both Ash and his twin on their Pokemon journey. Another character could be Misty. She could be friends with both of them and offer her own unique perspective on Pokemon training.
Misty and Brock could be important characters as well. They have been with Ash for a long time. They might be deeply affected by Ash's supposed death and be the ones leading the search to find out what really happened.
Team Rocket might be main characters as well. They could be constantly trying to capture Ash or his Pokemon because of his special status. Their bumbling attempts to take advantage of Ash's link to Arceus could add a lot of comical and action - filled moments to the fanfiction. And of course, Arceus itself could be a major character, guiding Ash in some way or interacting with him directly.
Well, perhaps in the fanfiction, Ash fakes his death to escape from some sort of unwanted fame or pressure. He's been in the spotlight for so long, and he just wants a break. So, he devises a plan to make it seem like he's passed away. Then he could start a new life in a different region, maybe with a new identity, and train Pokémon in a more peaceful and private way. He could also use this opportunity to learn more about some rare and elusive Pokémon without the media or his fans constantly following him.
Brock could also be a main character. Since he has knowledge about Pokémon care and breeding, he could be Ash's colleague in the fanfiction. They could work together on projects related to Pokémon health and nutrition.
The OC themselves are often popular characters. Since they are original creations, they can have all sorts of unique personalities, abilities, and backstories. For example, an OC could be a shy but brilliant Pokemon trainer who gradually overcomes their insecurities with Ash's help.
Misty and Brock are also main characters in many of these fanfictions. After Ash's sacrifice, they might be the ones to comfort Pikachu and the other Pokémon. They could also take on Ash's unfinished tasks, like continuing to explore the Pokémon world, helping other trainers, and fighting against any emerging threats. Their friendship with Ash gives them the motivation to keep going in his absence.
Latios would obviously be a key character. Also, Pikachu, Ash's loyal Pokémon partner, would be there. Maybe Misty or Brock could also be part of the story, with them either supporting or being skeptical of Ash's newfound admiration for Latios.