Mushishi is an anime about these supernatural beings invisible to a normal human and a guy named Ginko. These beings, called a Mushi, exist with no real purpose to life but just to exist, much like how there are bacteria, doing their thing, etc etc...
But anyway, Ginko is a Mushishi, which is something you can call an expert of these supernatural beings. The anime basically revolves around Ginko, the Mushi, and spontaneous stories of several different people who face problems relating to the Mushi.
Not much more to say about this anime. It's pretty slow-paced, and... oh, this anime is more of a horror series than a slice-of-life, although, it's nothing like Freddy Vs. Jason or anything like that...
A great anime for people who like sentimental stories.
Since this isn't licensed, and if anybody's interested, here's a link to the fansub group who distributes the anime. Bittorrent is a necessity.