Another interesting plot could be a time - travel story where Ash and Cynthia are sent back in time to the early days of the Pokémon world. They have to adapt to the different rules and ways of training Pokémon back then while also trying to find a way back to their own time.
Another plot could be set in a world where a strange phenomenon is affecting Pokémon. Ash and Cynthia join forces to investigate. Along the way, they discover a new type of Pokémon evolution that has been hidden for centuries. As they work together, they start to develop a deep friendship that might turn into something more.
Another plot could be that Ash enters a high - stakes Pokémon tournament in Cynthia's region. Cynthia becomes his mentor, teaching him advanced strategies, and they develop a strong friendship along the way.
One plot idea could be that Ash is captured by a new and powerful villain who wants to use his Pokémon knowledge for evil. Another could be that he's captured by a group who mistake him for someone else and he has to prove his identity while trying to escape. Maybe he's captured by an ancient Pokémon that has some sort of grudge against trainers and he has to convince it that not all trainers are bad.
A possible plot could be that a magical event causes Ash and Cynthia to be magically linked to a baby in a mysterious way. They have to travel to different regions to find a way to break the link if they want to continue their normal lives. But during this journey, they start to form a strong bond with the baby and question if they really want to break the link after all.
Another plot could involve a Pokémon contest where May is a contestant and Ash is there to support her. But something goes wrong with the contest rules due to a villain's interference. Ash and May then team up to expose the villain and make sure the contest is fair for all the contestants. It could also be a chance for their relationship to grow deeper as they face challenges together.
One idea could be Ash encountering a Legendary Pokemon that has lost its memory. Ash then tries to help it regain its memories while protecting it from poachers. Another could be a time - travel plot where Ash is sent back in time and has to team up with a Legendary Pokemon to prevent a great disaster from happening in the past that would change the future of the Pokemon world.
Perhaps in the fanfiction, Cynthia could be mentoring Ash in some advanced Pokemon battling techniques. Ash, being eager to learn, follows her guidance and in the process, they develop a deeper bond. This could lead to them exploring new regions together in search of rare Pokemon for training.
Perhaps Ash gets a special ability from a Legendary Pokémon, like the ability to communicate telepathically with all Pokémon. This causes him to be hunted by an organization that wants to use this power for their own gain. With the help of various Legendary Pokémon that he befriends on his journey, Ash has to protect himself and his new power.
A really interesting plot might be that Ash is chosen by an ancient dragon deity to be its champion. As a Dragon Master, he has to go on a quest to collect special dragon orbs scattered across different regions. Each orb gives him new powers or abilities related to dragon Pokémon. Along the journey, he faces challenges from other trainers who also want the orbs for their own purposes.
Maybe their journey takes them through a region where Pokémon are behaving strangely due to an environmental factor. Ash and Cynthia have to work together to figure out what's wrong and how to fix it. They could meet new Pokémon species along the way and make new friends who help them in their quest.