Well, it depends on where you look. Some smaller, niche fanfic communities might also have 'edgar figaro x relm fanfic'. You should start by doing a simple Google search with the keywords 'edgar figaro x relm fanfic' and then explore the results. Just be cautious of the sources to avoid any inappropriate or untrustworthy content.
First, get to know the characters well. Study their personalities, backstories, and how they interact in the original work. Then, come up with an interesting plot idea that could involve their relationship. For example, you could write about an adventure they go on together.
A prevalent theme can be the exploration of different cultures or settings. For example, if Edgar Figaro is crossed with a story set in a historical period, they have to adapt to that new environment. Also, power - dynamics can be a theme. If they cross with a more powerful character or group, they have to figure out their place in that hierarchy.
Sure. One great place to start looking for Edgar Figaro crossover fanfiction is Archive of Our Own (AO3). Just search for 'Edgar Figaro crossover' on their site and you'll find a variety of works. Some might cross Edgar and Figaro with other popular series like Final Fantasy or Persona, creating really interesting new storylines and character interactions.
Often, there's a theme of self - discovery. As they interact with each other, both Edgar and Lydia might learn more about themselves. For example, in some fanfics, Lydia might discover a new side of her personality through her relationship with Edgar. There can also be a theme of family, like if they come from different family backgrounds and how that affects their relationship.
Love against all odds is also a frequent theme. Maybe they come from different social classes or have families that don't approve. But they still fight for their relationship. This adds a lot of drama and makes the story engaging.
I don't think it's based on a true story. It seems to be a creation of the writer's imagination. Maybe it takes some elements from real life but not a direct retelling of actual events.