The fanfic could focus on Ash and Froakie's bond in Kanto. Maybe they get separated in a dense forest in Kanto and have to find their way back to each other. Along the way, Froakie discovers its hidden strengths and Ash learns more about the unique Pokémon in Kanto that he hadn't known before.
Perhaps Ash is called to Kanto for a special Pokémon event. While there, he stumbles upon Froakie being bullied by some other Pokémon. Ash steps in to protect Froakie and they immediately form a connection. Then they set off on an adventure across Kanto.
I'm not sure of a specific 'ash starts with froakie fanfic' off the top of my head. But you could try searching on fanfiction websites like FanFiction.net or Archive of Our Own. They have a vast collection of Pokémon - related fanfics, and you might be able to find one that meets your criteria.
One possible plotline could be Ash and Froakie's journey to become stronger together. They might face various challenges in Pokémon battles and overcome them with their bond. Another could be Froakie having some special ability that Ash helps it to discover and master.
One interesting plot could be that Ash and Froakie have a special bond from the start that allows them to communicate telepathically. They use this to outwit stronger opponents in battles and quickly rise through the ranks in the Pokemon League.
The 'ash kanto fanfic' is interesting because it allows for a deeper exploration of Ash's character in the Kanto region. It can show his growth and development in ways that the original series might not have fully covered.
One key element is Ash's character development. He should grow from his experiences in the league. Another is his Pokémon team. Each Pokémon should play a crucial role in his victory. For example, Pikachu's speed and electric attacks could be a deciding factor. Also, the rival trainers are important. Their different strategies and Pokémon make the battles exciting. Ash has to outwit them to win.
A common theme is friendship. Ash forms many bonds with his Pokémon and fellow trainers during his Kanto journey, and fanfics often explore these relationships further. Another theme is growth. Fans like to write about how Ash develops as a trainer in Kanto, learning new battle strategies and becoming more confident.
Well, in the 'ash goes back to kanto fanfic', it could be that Ash goes back to compete in some special Kanto - only Pokémon battles. He might meet some of his old rivals and have epic rematches. He could also discover new secrets about the Pokémon in Kanto that he didn't know before, like hidden abilities or unique evolutionary paths. And of course, he would probably share his experiences from other regions with the people in Kanto.