The death of a Pokémon he's close to. Pokémon are like family to Ash, and if he were to lose one, especially in a tragic way, it would be a huge emotional blow and would likely make him cry. For example, if Pikachu were to sacrifice itself to save Ash from a powerful enemy.
His rival, Gary, could be a likely candidate. Gary has always been competitive with Ash, and in this fanfiction, his jealousy could reach a boiling point, causing him to betray Ash for his own gain, like trying to steal his Pokémon or get credit for his achievements.
A possible plot could be Ash visiting an old, abandoned Pokémon sanctuary. He explores the place quietly, feeling a sense of melancholy. As he walks through the overgrown paths, he discovers an injured and rare Pokémon. He then uses his knowledge and skills in a very calm and methodical way to nurse it back to health. This shows a different side of Ash, one that is more patient and less about the big battles.
It could be a famous Pokémon trainer. Maybe someone who has traveled to many different regions and has a lot of knowledge about rare Pokémon.
One possible plot could be that a villain uses hypnosis on Ash Ketchum to make him do their bidding in Pokémon battles. So instead of using his own strategies, he's forced to follow the commands of the hypnotist. This would create a lot of chaos and challenges for his friends as they try to figure out what's wrong with Ash and how to break the hypnosis.
One possible plot could be that Naruto, with his ninja skills and determination, takes on the Pokemon world as Ash. He might use his combat experience to develop unique battle strategies in Pokemon battles. For example, he could incorporate his shadow clone jutsu in some way, like using clones to distract opponents' Pokemon while his own Pokemon attacks from an unexpected angle.
Well, one possible plot could be that Ash, while on his Pokémon journey, somehow stumbles into the wizarding world. Harry Potter then takes Ash under his wing and shows him around Hogwarts. Ash could introduce his Pokémon to the students at Hogwarts, and they could all work together to solve a mystery that involves both magic and Pokémon powers. Maybe there's a dark wizard who wants to use Pokémon for evil purposes, and Harry and Ash have to stop him.
Well, it could be really exciting. Ash already has his Pokémon journey skills, and adding the Force to it would make him super powerful. He could use the Force to sense where rare Pokémon are, or to communicate with them on a deeper level. Maybe he could even use it to enhance his Pokémon's abilities during battles, like giving Pikachu an extra boost of speed or power.
One thing that could inspire such a fanfiction is Ash's growth as a character. In the original series, he has grown in terms of his skills as a Pokemon trainer. Expanding on that, the idea of his physical growth, like muscle growth, could be a natural progression. Maybe he faces a new rival who is not only strong in terms of Pokemon battles but also physically intimidating. This could drive Ash to work on his own physical strength. Another inspiration could be if he enters a new tournament that has physical challenges as part of the preliminaries. To compete, he has to build muscle.
One possible storyline could be that Ash has to go undercover in a dress for a special mission. Maybe he's trying to infiltrate an all - female Pokémon training group where men are not allowed. So, he dons a dress to blend in and learn their secrets.
One possible plot could be that the OC, now as Ash, has all the knowledge from their previous life. They might use this to train their Pokémon more effectively. For example, they could quickly figure out the best training regime for Pikachu, making it even stronger than in the original series. They could also have different strategies in Pokémon battles, using their prior knowledge of different Pokémon types and moves to their advantage.