A common theme could be the male human's quest to protect the female Pokemon. In many Pokemon stories, there are threats from other Pokemon or humans who might want to harm or capture the female Pokemon. The male human, being the protector, would use his skills and knowledge to keep her safe.
To write their interaction realistically, first understand Mew's nature. Mew is a very intelligent and curious Pokemon. So, the male human could start by showing respect for Mew's space and abilities. For example, when they first meet, the human doesn't try to capture Mew but rather offers some food or a friendly gesture. Then, as they interact more, they could exchange knowledge. The human could tell Mew about human culture, and Mew could share some of the secrets of the Pokemon world.
The story could be set in a post - war scenario where the male human and the female arbiter are part of a reconstruction effort. They have to work together to rebuild a planet that was destroyed during the war. Their relationship starts off as a professional one but as they face difficulties like resource shortages and hostile survivors, they grow closer. They learn to rely on each other's skills, with the male human's engineering skills and the female arbiter's leadership abilities complementing each other.
A simple interaction could be that the female human is a hunter. One day, she encounters the male sabercat while it's hunting the same prey. Instead of fighting over it, they somehow come to an agreement. Maybe the sabercat allows her to have a share of the prey in return for her helping it defend its territory from other predators later.
One idea could be a story where a male human is on a journey through the Pokémon world and encounters a Salazzel. They start off as foes but gradually develop an understanding of each other. Maybe the male human is a trainer trying to find a rare Pokémon and Salazzel initially sees him as a threat to her territory.
In such fanfiction, the male human character might have to overcome various challenges with the female Pokemon by his side. For example, they could face a powerful and evil Pokemon organization. The fanfiction could focus on how their different abilities and personalities complement each other in the fight against the bad guys. The female Pokemon might have unique powers like the ability to heal or a special attack that the human can strategize around.
To develop their interaction, start with an encounter. For instance, a male human could be on a quest in Skyrim and stumble upon the female sabercat's lair. Their first reaction could be one of wariness. Then, a small act like the human leaving some food for the sabercat can start the bond. As they meet more often, they learn about each other's behaviors.
A possible fanfic plot could involve the female Charizard being a sort of guardian of an ancient and mysterious place. The male human stumbles upon this place and initially, the Charizard is hostile. But as time passes, they realize they have common goals in protecting the secrets of the place. Their relationship then develops into a deep friendship, with the human learning about the Charizard's world and the Charizard learning about human emotions.
Their interaction could be quite interesting. Ash would likely be cautious at first because Tyranitar is a large and powerful Pokemon. But his kind nature would soon make him approach it gently. The female Tyranitar might be initially skeptical of Ash but then grow to trust him as he offers her food or helps her when she's injured. They could communicate through body language and Ash's understanding of Pokemon emotions.
It could be a story of transformation. The female human, through some magic or ancient ritual in Skyrim, might be able to transform into a form that can better communicate or interact with the male sabertooth. This new form could bridge the gap between their two species, leading to a series of adventures where they both learn from each other and grow as individuals.
One common theme is the power of friendship that evolves into love. For example, in many stories, the male human and the female pokemon start off as just friends or trainer - pokemon partners. Another theme is the acceptance of differences. Since they are from different species, they have to accept each other's unique qualities. Also, adventure is often a theme as they usually go on journeys together in the Pokemon world.