A plot could start with Latias being in some kind of danger, and Ash comes to her rescue. This leads to them spending more time together. As they get to know each other better, they realize their feelings are more than just friendship. After getting married, they might have to deal with people or Pokemon who don't approve of their relationship at first. But through their kindness and the strength of their love, they win them over and continue their happy life together.
Ash could catch Latias in a place full of ancient ruins. Latias might be guarding some sort of Pokemon relic there. Ash shows respect for the place and Latias' role. This makes Latias interested in him. Eventually, Ash catches Latias and they go on to discover more about the relic's power together.
Yes, there are some out there. You can start by looking on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'pokemon ash and latias married' in their search bars, and you should be able to find some stories. However, the quality may vary, so be prepared to skim through a few to find one that suits your taste.
One possible plot could be that Ash and Ursula meet during one of Ash's travels. They start off as rivals but gradually develop feelings for each other. After many adventures together, they decide to get married. Their wedding could be attended by all their Pokémon friends, and they might start a new life exploring new regions as a married couple.
In this fanfiction, it could be that Ash's marriage is a way to bring peace between different regions. He marries a princess or a powerful trainer from a rival region. Their union symbolizes the unity of Pokémon trainers everywhere. The story could then detail the political and social implications of their marriage, as well as the more personal aspects like their relationship building and how they learn to love and respect each other's Pokémon.
In this fanfiction, it might be that Latias controls Ash as part of an experiment. Latias is a curious Pokémon and wants to see how a human like Ash would react in different scenarios. So she uses her powers to make Ash explore areas he might not have otherwise, like a hidden and mysterious part of the Pokémon world. This could lead to Ash discovering new Pokémon species or even new types of Poké Balls. As he's being controlled, his initial fear turns into a sense of adventure as he experiences things he never thought possible.
One possible plot could be that Latias discovers she is pregnant and has to hide from some villains who might want to harm her unborn child. She could then seek help from other friendly Pokemon or trainers.
One plot idea could be them training a new and rare Pokemon together as a married couple. Another could be them hosting a Pokemon tournament in their hometown.
The fanfiction of Ash and Latias' love often takes the readers on a journey of emotions. It can show the evolution of their relationship from simple acquaintance to deep love. Some fanfictions may include other Pokemon characters reacting to their relationship. Maybe Pikachu would be supportive, or some other jealous Pokemon might try to come between them, adding more drama to the story.
In Pokemon Ash and Latias fanfiction, the writers can also play around with the idea of Latias being a key to unlocking new regions or powers within the Pokemon universe. Ash, being the curious and adventurous trainer he is, would be eager to explore these new possibilities with Latias by his side. It's a great way to expand on the existing Pokemon lore and create exciting new storylines.
In some fanfictions, Ash and Latias might team up to protect a special place or a group of Pokemon from a powerful threat. Their combined skills - Ash's battle experience and Latias's psychic abilities - would make them a formidable duo. This kind of plot not only showcases their bond but also creates a lot of action - packed and thrilling moments in the story.