As a Mew fan, Ash might start to study different aspects of Pokémon lore more deeply. This could make him wiser in the ways of Pokémon. He could also develop a more empathetic side towards Mew - like Pokémon, seeing them as not just creatures to battle with but also as beings with their own unique qualities and stories.
Well, it could have some really cool plots. Maybe Ash has some secret admiration for Mew that leads him on all kinds of hidden adventures or self - discovery. He might be trying to protect Mew in secret or has a special connection with it that no one else knows about.
Ash could become more patient. Since Togepi is a relatively weak and cute Pokémon at first, Ash has to be patient in training it. This would be a change from his sometimes impulsive nature in battles.
Ash might develop a deeper sense of responsibility. In a fanfiction, if he is in charge of protecting Manaphy, he would have to think more about the consequences of his actions. He could also learn to be more diplomatic, especially when dealing with May's different approach to Pokémon. May could grow in her ability to adapt. For example, if they end up in a situation where there are no contests but only battles, she could learn from Ash how to handle it. Manaphy could develop its psychic abilities further. Maybe it discovers new powers within itself while being with Ash and May, and they help it to control and use these powers for good.
Ash could become more understanding of different training methods through Daisy. Maybe he learns from her how to better communicate with his Pokemon on an emotional level.
Ash could develop his ability to understand different Pokemon cultures better. Cynthia, being from a different region, has a lot of knowledge about various Pokemon traditions. Ash could learn from her and in turn, teach her about his own experiences. This exchange could make Ash more worldly and Cynthia more in touch with the broader Pokemon community. In terms of their relationship, they could start to rely on each other more, which would be a big step for both of them character - wise.
Ash could become more mature. In a love - centered fanfiction with Cynthia, he might start to think more about the future and less about just the next Pokémon battle. His relationship with Cynthia could make him more strategic as he learns from her.
Ash might develop a deeper understanding of different training styles. Bianca has her own unique way of training Pokemon in the Unova region, and through their interactions, Ash could incorporate some of her ideas into his own training. Bianca, on the other hand, could become more adventurous. Ash's tales of his travels could inspire her to explore more areas in Unova and take on greater challenges. Their relationship could also lead to both of them becoming more empathetic towards others, as they support each other through various difficulties.
Ash might become more confident. Knowing he's the son of Sir Aaron could give him a boost in self - esteem. He could also become more mature as he tries to live up to his father's reputation.
Mew often interacts with Ash in a very friendly and helpful way. Since Mew is a very powerful and intelligent Pokémon, it might guide Ash in his journey. For example, it could show Ash shortcuts to new Pokémon areas or give him advice on how to handle difficult Pokémon battles.
One possible plot development could be that Naruto discovers his deafness gradually and has to hide it from his enemies. He might be afraid that they would use it against him in battle. Another could be that his friends find out by accident and have to learn sign language to communicate better with him.