Obviously, Ash is the most important character as the story revolves around his death and return. Pikachu is also crucial as his closest pokemon companion. His friends like Misty, Brock, and Serena would play significant roles as they would be affected by his death and overjoyed at his return.
The other trainers in Pallet Town might look up to him even more now. They could gather around him, asking for stories about his battles and the rare Pokémon he's encountered. It would be a great opportunity for Ash to pass on his experience.
In such a fanfiction, a common plot point could be the shock and grief among Ash's friends when he dies. Maybe Pikachu refuses to leave his side at first. When he returns, he might have some new powers or a different perspective on his pokemon journey.
Perhaps he'll share his new adventures and the knowledge he's gained from traveling different regions. He could inspire the new generation of Pokémon trainers in Pallet Town to aim for greater things.
Pikachu is a very likely candidate. It's Ash's most iconic Pokemon and has a deep bond with him. Whenever Ash is in trouble, Pikachu often steps up to protect him.
There could be unfinished business between them. They might have a shared goal that they haven't achieved yet. Greninja's return to Ash in the fanfiction could be to finally complete that goal, whether it's winning a particular Pokemon tournament or saving a certain place from destruction.
Ash could be a Pokémon trainer with a different starting point in this fanfiction. Born in 1987, by 1997 he might have already made a name for himself in local Pokémon battles. He could have a team of Pokémon that he rescued from difficult situations, like a Charmander that was abandoned by its trainer. His story could revolve around giving these Pokémon a second chance and proving that Pokémon don't need to be 'perfect' to be strong.
The impact of Ash's loss in the fanfiction could extend beyond just himself. His Pokémon might also feel demoralized. However, this could also be an opportunity for them to grow stronger together. Ash could start training more intensively, seek new training methods, or even try to catch new Pokémon to strengthen his team.
For Ash, Pikachu is always a great choice as it's his most loyal and powerful partner. Alongside that, a strong flying type like Charizard could be useful. For Brock, his Onix would be a staple. And perhaps a water - type like Vaporeon could be good for him to balance his team. Since they are teaming up, having a psychic - type like Alakazam could also be beneficial as it can help in battles and also with communication in tricky situations.
Ash could also have Charizard. It's a powerful and well - loved Pokemon of his. It could provide a lot of firepower in battles. For Gray, a Glaceon would be great. Glaceon's ice - type moves could complement Gray's more strategic style. It could freeze opponents and give Gray time to plan his next move.