In this fanfiction, Ash could be on a solo adventure when he stumbles upon a Latios that is being chased by poachers. Ash uses his Pokémon to fend off the poachers and saves Latios. In gratitude, Latios decides to accompany Ash on his journey. As they travel together, Latios starts to share its knowledge of rare Pokémon and hidden places with Ash. But soon, they face a powerful trainer who wants to capture Latios, and Ash has to fight to protect his new friend.
Well, perhaps Ash starts his journey in a new region where Latios is a legend. He has a strange encounter with Latios in a dream first. Then, one day while exploring an ancient ruin, he actually meets Latios. Latios seems to be drawn to Ash for some reason. Ash then learns that Latios is trying to prevent an evil team from awakening an ancient evil Pokémon. Ash and his friends then team up with Latios to stop this from happening.
One possible plot could be that Ash meets a Latios in a mysterious forest. Latios is injured, and Ash decides to help it. As he nurses it back to health, they form a strong bond. Ash then discovers that Latios has a special mission related to protecting a hidden power in the forest. With the help of his Pokémon, Ash joins Latios on this mission, facing various challenges along the way.
Maybe a mysterious organization that wants to experiment on Latios. They believe that Latios holds the key to some sort of genetic or power - enhancing technology. They send out their agents, who are skilled in Pokémon capture and combat, to try and get Latios. They don't care about Ash at first, but when he stands in their way, they see him as an obstacle to be removed.
A plotline might be that Latios is from a different dimension or time, and it has come to Ash's world for a specific purpose. Ash gets involved in this mission, and together they have to face powerful enemies. This could introduce new Pokémon species from other dimensions and new battle strategies that Ash has to learn to keep up with the challenges.
The plot could start with Ash stumbling upon an ancient artifact or a cursed place. As he touches or enters it, he is suddenly transformed into Latios. At first, he struggles to control his new form and powers. He might accidentally cause some chaos in the Pokémon world. His friends then set out to find a way to turn him back. Along the way, they encounter various obstacles and meet other Pokémon who either help or hinder their quest.
Maybe Ash gets magically transformed into a Latios. He then discovers he can fly and uses his new powers to explore regions he couldn't reach before as a human. He might also meet other Pokémon in a different way and form new friendships.
A possible plot could be that Latios is from a different dimension and somehow ends up in Ash's world. Ash is the only one who can understand Latios' distress signals. They embark on a journey to find a way to send Latios back home. Along the way, they encounter many challenges and make new friends, both Pokemon and human. Ash also discovers new types of Pokemon battles and strategies from Latios, which he later uses to compete in his own Pokemon league.
In this fanfiction, Fem Ash could be lost in a strange dimension. Latios, sensing her distress, comes to her rescue. He tries to communicate with her, which is difficult at first. But as time passes, they find a way to understand each other. Latios then guides her through the dimension, showing her amazing sights and introducing her to unique Pokémon. By the end, Fem Ash is sad to leave the dimension and Latios, but they promise to meet again.
The plot might involve Ash being given a Latios egg as a starter. As he hatches it, he realizes the great power and potential within Latios. They then embark on a journey to explore different regions. Along the way, Latios helps Ash understand the deeper connection between Pokémon and humans, and they encounter rare Pokémon that only Latios's unique abilities can detect.
Well, I haven't really read a particular 'ash starts with latios fanfiction' myself. However, if you join some Pokémon - related fan groups on social media platforms, like Pokémon fan clubs on Facebook or Reddit communities dedicated to Pokémon fanfiction. You could ask the members there if they know any good ones. They are often very helpful in sharing their favorite fanfictions.
A possible plot could be centered around the mystery of Latios. Since it's a very special Pokémon, there could be ancient secrets associated with it. Ash, with Latios as his starter, would be on a quest to uncover these secrets. Along the way, they would face other trainers who are envious of Ash having such a powerful Pokémon. Ash would have to prove that he is a worthy trainer of Latios through his skills and the bond they share.
Perhaps in this fanfiction, Ash goes to the town in search of a rare Pokemon item. But when he arrives, he discovers that Latias and Latios are in trouble because of some evil forces. So, Ash decides to help them out. He uses his battle skills and knowledge of Pokemon to fight against these forces. Along the way, he also learns about the unique culture and traditions of the town.