Genre confusion: Mystery

Finding a clear definition for this genre is kind of difficult. Usually the genre refers to stories of a person solving a crime without any personal gain and without any supernatural power involved.

I can only explain the way we use the term in Germany - and it actually would make sense if it'd be used in a similar way in other countries but maybe the meaning changed after we adopted the English word into German - but since I'm not sure about this I think I definitely should define this term on here.

The easiest way to describe mystery we use is more like a mix of horror and fantasy, that also works with elements of science fiction from time to time. A differentiation is the easiest if we look at how the series deals with the 'supernatural' phenomena. In the mystery genre, there's usually some kind of ambivalence between description and perception as well as an ambivalence between backgrounds and motives.
Compared to horror, the weirdness is rarely shown or in a different way. The human protagonists are more important, as well as the way they think about the happenings. That's why we usually see a rather subjective perception. That makes the genre seem closer to thriller than horror.

In Asian dramas, I usually use the genre because of 'mysterious' happenings - that works quite well for Secret Investigation Record but also for The Master's Sun. Especially in the latter one we find the subjective perception of the female lead character who's able to see ghosts. Choosing between mystery and simple fantasy is the most difficult in those cases but since the supernatural seems more threatening to the people (at least at first) I'd go with mystery.

I'm still sure it's difficult to define and everyone has to do this on their own since there are no clear lines between genres in general.