Ok so this fanfiction idea is a LONG way off (I have to finish my RWBY fic first) but I'm planning on writing a short Atelier Ryza fanfiction that's mostly character interaction but a little bit of what happens in the games too. In the game there's a Near extinct race called the Oren, they haven't really hinted that there's 'more' of them, but they haven't said that these three (yes there's only three of them across both games) either. They've been intentionally vague about the race, only explaining what needs to be explained for the plot. Would it be strange for another Oran to exist that don't happen to be in the games? Keep in mind I'm not adding like, an entire clan or anything, just the one like how the games have only been introducing one. I'd like to use an Oran character but none of the available Oran characters fit the bill.
No. If you make It plausible, then nothing is too strange. Look at "Guardians of the Galaxy", does a talking tree and a talking Racoon seem strange? Oh yes. But we, as the audience, accept it.
You just have to sell it well enough for someone to want to sit down and read it. I've read some really weird sh*t in my life and some of it I laughed through. Partly because it was so ridiculous, and partly because the author was really good at pulling it off.