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 a fanfiction, Ash might have a special bond with Latios. Maybe Latios senses Ash's pure love for Pokemon and decides to team up with him. They could go on adventures, facing powerful foes together. Ash could learn new techniques from observing Latios in battles.
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.
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.
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.
One idea could be that Ash forms a special bond with Latios and Latias while on a journey in a new region. They help him discover a hidden power within himself. For example, Latios might be able to sense when Ash is about to make a wrong move in a battle and communicate it to him telepathically.
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.
Through shared adventures. For instance, if they get lost in a mysterious forest together. Ash would rely on Latios or Latias's ability to sense their surroundings and they would grow closer as they face the challenges of finding their way out. It could be as simple as Ash sharing his food with them during this time, showing kindness.