One possible plot could be that Ash and Leaf embark on a journey to find a rare and powerful Pokémon. Along the way, they face numerous challenges like difficult terrains and powerful rival trainers. They also discover secrets about an ancient Pokémon civilization.
Well, a plot could involve Ash and Leaf teaming up to participate in a special Pokémon tournament that's held in a far - off region. During their journey to the tournament, they encounter Pokémon with unique abilities they've never seen before. They have to figure out how to train and use these Pokémon to their advantage in the tournament. And in the process, their friendship grows stronger as they rely on each other's skills.
A really interesting plot for an 'ash and leaf journey fanfiction' might be that Ash and Leaf receive a mysterious message that leads them on a journey. The message seems to be related to a prophecy about two trainers who will save the Pokémon world from an impending disaster. As they travel, they meet other trainers who either help or hinder them. They also have to deal with their own insecurities and doubts. For example, Leaf might doubt her own abilities compared to Ash's more well - known skills. But through their journey, they both grow and become more confident in themselves and their partnership.