What could happen in 'Ash travels Kalos after Alola fanfiction'?

He might meet Serena again. Since he has been to Alola and now travels to Kalos, their reunion could be an interesting plot point.

Well, one possible plot could be that in the Kalos region, Ash makes a new powerful rival. Haruka, being in Kalos for some reason, gets influenced by this rival's charm and power. In Alola, Ash discovers that Haruka has been secretly helping this rival against him, thus feeling betrayed. Maybe the rival promised Haruka something she couldn't resist, like a rare Pokémon or a chance to become a top - tier trainer in a different way.

The antagonist could be a powerful and devious Team Rocket member who has infiltrated the Kalos and Alola regions. This member could manipulate Haruka, perhaps by blackmailing her with something from her past in Kalos. In Alola, the Team Rocket member uses Haruka to get to Ash, making her betray Ash without really wanting to.

They could participate in the Kalos League. Ash's determination and Dawn's strategic thinking would make them a formidable team. They might also discover new Pokemon evolutions specific to Kalos and use them to their advantage in battles.

Ash could discover a new form of an existing Alola Pokemon. This new form could be the result of some kind of special evolution due to the unique energy in the Alola region. His friends would be amazed, and they would all help him research and understand this new discovery.

Well, perhaps Greninja will encounter some new and strange Pokémon in Alola that it has never seen before. Ash could use this opportunity to train Greninja further, and they might participate in some Alola - specific Pokémon contests or battles together. Greninja's presence could also stir up some friendly rivalries among the local Pokémon and trainers, leading to exciting adventures and growth for both Ash and Greninja.

In this kind of fanfiction, they might have new adventures. They could explore the unique Alola region together, encounter new Pokemon species, and bond even more deeply. Maybe Serena would learn new battle strategies from Ash, and they would participate in local Alola Pokemon contests and battles side by side.

Ash and Anabel could go on a Pokemon-catching spree in Alola. They might compete to see who can catch the rarest Pokemon first.

One possibility is that they could explore the beautiful Kalos region together. They might visit all the different gyms that Ash didn't get to fully experience before. Serena could also introduce Ash to more of the local cuisine and they could have picnics in the scenic areas of Kalos. Maybe they'd even participate in some local festivals and make new friends together.

In this fanfiction, Ash might make new friends in the Alola region. He could encounter unique Pokémon there that he has never seen before, like the Alola forms of some Pokémon.