Well, in fanfiction, they might have an epic Pokémon battle. Ash could show off his unique battle strategies that he's developed over his journey, and Cynthia would bring her powerful Pokémon and tough battling skills. Maybe Ash's Pikachu would face off against Cynthia's Garchomp, creating a really exciting and intense showdown.
It could be a jealous fellow trainer. There are always those in the Pokémon world who envy the skills and achievements of others. This trainer might see Ash and Cynthia as obstacles to their own glory and decide to betray them to get ahead.
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.
Well, it's possible that Ash and Mewtwo team up in the fanfic. They could face a common enemy together. Mewtwo's incredible psychic powers combined with Ash's experience and determination would make them a formidable duo. And perhaps this encounter would change Ash's view on some things, like the true nature of Pokémon battles.
Perhaps in the fanfic, Ash has achieved a lot in his Pokémon journey, and Misty has also become a more skilled Pokémon trainer. When they meet again, they start to compare their experiences. Ash could show Misty his new and powerful Pokémon, and Misty could introduce Ash to some new training techniques she has learned. And then they decide to train together for a while to improve their skills even more.
They would become more united and responsible. Their relationship would shift from just being friends or fellow trainers to co - parents. They would need to communicate more about the baby's needs, like what kind of Pokemon - related education to give the baby.
It could be that Mewtwo is on a quest to find its true origin or purpose. Ash joins Mewtwo on this journey. Along the way, they meet other powerful Pokémon and trainers. There are battles and competitions, but also moments of self - discovery for both Ash and Mewtwo. The fanfic might explore themes of identity, friendship, and the power of Pokémon in a more profound way through this plot.
Maybe a mysterious organization that is trying to capture all the Pokémon in the area where Ash and Misty meet again. They would be the antagonists as Ash and Misty would try to stop them. This organization might have some powerful Pokémon and devious plans that Ash and Misty have to figure out and defeat.
Ash could be a heroic or central character who drives the action in the story. Cynthia, on the other hand, may be a supporting character who helps Ash in his journey or is the recipient of whatever the 'ash cums inside' event symbolizes. For example, if it's about Ash bringing a new concept or power, Cynthia could be the one who helps him understand how to use it properly within the context of the fan - created world.