According to the Urban Dictionary, Mushi means Dragon in old Asian language but of course it fails to specify what Asian language. *eye roll*
Mushi in this book refers to a supernatural being/spirit/thing/
whatchamacallit that has been around since the dawn of time. They cause all kinds of horrible afflictions to humans however. The lead character Ginko is what it's known as a Mushishi. A sort of monk who travels around dispelling Mushi from the bodies of humans. There are different kinds Mushi. So the bodies haunted by them suffer all kinds of different symptoms like horns growing out of their foreheads and overwhelming voices of the Mushi from all over the world.
This was labelled as a horror manga at the local library which is stupid because it's really not scary or graphic. hmm. It's labelled for 16+ readers, but I didn't really find anything explicit.
I have volume 2 and I'm gonna read it despite not finding the first one very compelling. As far as I can tell there are only 2 volumes but there is a 26 episode anime based on the stories.