In the fanfiction, Ash could be on a special quest to catch Tapu Koko. It could be related to saving the Alola region from some kind of threat. So, catching Tapu Koko becomes not just a personal achievement but also a way to protect the land and its people. He might need to prove himself worthy to Tapu Koko before it allows itself to be caught.
Some social media groups dedicated to Pokemon also might be a good place to look. People in these groups may have written or know of some fanfictions about Ash catching Tapu Koko. For example, Pokemon fan groups on Facebook or Reddit.
One possible plotline could be that Ash meets Tapu Koko in a mysterious forest. Tapu Koko is initially cautious of Ash, but Ash shows his pure love for Pokémon through his actions like sharing his food with other Pokémon. This earns Tapu Koko's trust gradually, and eventually Ash manages to catch it in a very unique Poké Ball. It could be a special one given to him by an elder in the Alola region.
His other Pokémon like Rowlet might be in awe. Rowlet is a curious Pokémon, and having a mythical Pokémon like Tapu Koko around would be fascinating. It could learn a lot from Tapu Koko, especially in terms of using its unique powers more effectively. The whole team would likely feel a sense of pride that Ash was able to catch such a rare and powerful Pokémon.
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.
In a fanfiction about Ash born in 1987 and his situation in 1997, we could see an alternate story where Ash is not the typical rookie trainer. Since he's a bit older than in the original, he might be more knowledgeable about Pokémon lore. He could be on a quest to uncover some ancient Pokémon secrets in 1997. He might travel to different regions, not just for battles but also to study old Pokémon texts and artifacts, and along the way, form an unusual team of Pokémon that are attracted to his in - depth knowledge.
There are also fanfictions where Ash catches Rayquaza. This could be set during a time when the sky is in chaos due to some dark energy. Rayquaza is drawn to Ash because of his pure heart and determination. Ash, with his usual courage, teams up with his pokemon to assist Rayquaza in restoring balance. As a result, Rayquaza allows Ash to catch it.
If we consider the common growth pattern in the Pokemon series, Charmander evolving into Charmeleon could be an early evolution in the fanfiction. Since Charmander has a clear evolution line and Ash has a strong bond with it, it would make sense for it to be one of the first to evolve, perhaps due to a tough battle or a special encounter that accelerates its growth.
Ash's loss could lead to a change in his journey. Instead of just aiming for Pokémon battles and championships, he might focus more on self - improvement and understanding his Pokémon better. He could travel to new regions to learn different training techniques or seek out wise Pokémon trainers who can give him advice on how to avoid such losses in the future.