Their relationship could become stronger as they rely on each other during the challenges of time travel. They might face dangerous situations where they have to protect one another, which would deepen their bond.
One idea could be that Ash and May travel back to the time when the first Pokemon were discovered. They could witness the first encounters between humans and Pokemon and learn about the origin of Pokemon battles. Another plot could involve them traveling to a future where Pokemon have evolved in unexpected ways, and they have to adapt to these new forms of Pokemon. Maybe they also meet their future selves and gain insights into their own destinies.
I'm not sure specifically as there could be many different versions of this fanfiction. But generally, it might involve Ash and May going on adventures through time, perhaps encountering different Pokemon species from various eras, facing challenges related to time - like fixing time - rifts or something.
A possible fanfiction plot could be that Ash, Serena, and May are invited to a mysterious island full of unknown Pokemon. They have to work together to survive and discover the secrets of the island. Ash's leadership, Serena's ability to communicate with Pokemon, and May's quick decision - making skills would be crucial.
In this fanfiction, Ash and May could be on separate adventures in Kalos at first. But then, they cross paths when they both get involved in a mystery related to a rare and powerful Pokémon in Kalos. They have to put their heads together, along with their Pokémon, to solve the mystery and protect the Pokémon from those who would use it for bad purposes.
In some fanfictions, Ash might develop a special bond with both Serena and May. For example, they could be exploring a new region together and encounter a rare Pokemon. Serena could use her knowledge of Pokemon behavior to track it, May could come up with a battle plan, and Ash would be the one to catch it. This kind of adventure would strengthen their friendship and show how well they work together.
It could be a rival trainer. Rival trainers are often very competitive in the Pokémon world. Maybe this rival is jealous of Ash and May's progress and decides to betray them to slow them down. They might spread false rumors about Ash and May, causing other trainers to be distrustful of them.
It could be a future version of Team Rocket. They might have become more powerful and devious in the future and travel back in time to stop Ash from achieving something important in the past that would prevent their future rise to power. Another option could be a time - traveling Pokemon hunter who wants to capture rare and powerful Pokemon from different time periods, and Ash stands in his way.
Well, it's highly probable. Given the popularity of Pokemon and the creative freedom in fanfiction, writers may come up with a story where Ash kisses May. You could start by looking at well - known fanfiction sites like FanFiction.net or Archive of Our Own.