dude, it's omegaverse, but called ying and yang instead of omega and alpha because that's how the medieval korea would've refered to it
I've seen omegaverses refer to alpha/omega as such in medieval Korean settings, so that lack of clarification is odd.
maybe it's just me that's seen it before, so I made the connection immediately. I thought of master from another world, where the modern day alpha gets isekai-ed into medieval times and explains that to himself, that that's how they were referring to the alphas and omegas.
Anyway it's un the tags too, and also it's quite inferred in the description
But you're right that it's more often referred as alpha omega in medieval settings then not, too
The whole "medieval gay couple free to get married" is an interesting concept, but I fail to see the logic of it unless they're able to start the family line as per tradition at that point in time. I'd be open to some mpreg for this.