Hm, yeah, it's kinda rough grouping a whole series into one genre label. XD ; Had that issue with mine.
I originally had it under Fantasy due to the supernatural elements present, and the fact that the world used to be more high-fantasy-ish back in its ancient ages... But now the magic's faded quite a bit by the time period the story takes place, to the point where people don't even think it's real anymore.
I ended up changing it to Mystery though due to the overarching mystery of the plot, and I felt that as a genre it ultimately fit the story more than just the setting.
That said, there's probably gonna be a mix of all sorts of little things, like comedy and drama and action, aaaand some romance, but yeah the mystery's one of the most central elements to the plot.
I guess supernatural could work for it too, given the whole curses and ghosts thing, but last I checked I think only webtoon had that as an option.