Alright, so Kody and Lumine? We're talking about mashing up a game I've never even played with an OC from... some other corner of the internet, right? Honestly, the appeal kind of escapes me. I see these crossovers floating around and it always feels like the author's personal D&D character got inserted into another world. The popular plots seem to default to 'Lumine finds this weird human in Teyvat' and then it's either instant romance or a slow-burn team-up against the Abyss Order. It’s fine, I guess, if you’re into that self-insert flavor, but it lacks the built-in tension of established Genshin pairings. Most fics I’ve skimmed lean hard on Kody being this mysterious outsider with secret knowledge, which can get repetitive. I’d probably read one if the writing was spectacular, but the premise itself doesn’t grab me.
That said, I did come across one that tried something different: Kody was an artifact from a lost civilization that Lumine had to reassemble, and their communication was purely through elemental energy pulses. Now that was a neat mechanic, turning the usual dialogue-heavy interaction into something visual and unique to the game's world. It didn't last long, the author abandoned it after three chapters, but it showed there's potential beyond the standard 'stranger in a strange land' trope if people are willing to get weird with it.