I've a specific concept in mind, however the details of the setting can be built together with my prospective partner for this.

Inspiration for the idea in general includes Gundam(Iron Blooded Orphans in particular), Dune, and a little Game of Thrones.

This is a sci fi world, but with an almost feudal system of government with noble houses serving under an empire(think Dune, if you're familiar).

An important weapon in this world is mecha. There are many that are used, but there's also a special higher classification(think gundams vs ordinary mobile suits). Most(if not all) of that higher class are owned by noble houses, but there's something about them that makes it so they "choose" their pilot, and many of them sit in storage because the houses that own them haven't found a pilot from within the family.

Your character will be the heir to one of these houses, my character will be an ordinary mecha pilot, who is discovered to be compatible with your family's special mecha. The family quietly arranges a marriage between the two characters, so that mine is technically a member of the family, and is therefore allowed to pilot it.

The RP would have a background of war and court intrigue, with this fake marriage in the foreground.

So we would have a fake marriage trope, with possible enemies-to-lovers.

A lot of the details are up for us to decide in a pre-game world building phase.

I'm not set on the gender of either character.  I'm not even set on them both being human, or even the same species as each other, if we decide this takes place in a world with aliens.

If you're interested, send me a DM, and let me know what kind of character you intend to play, as well as what you'd like to get out of the story.