(Source - Wiki)

Plot Summary: They are neither plants nor animals. They differ from other forms of life such as the micro-organisms and the fungi. Instead they resemble the primeval body of life and are generally known as "Mushi". Their existence and appearance are unknown to many and only a limited number of humans are aware of them. Ginko is a "Mushi-shi" who travels around to investigate and find out more about the "Mushi". In the process, he also lends a helping hand to people who face problems with supernatural occurances which may be related to the "Mushi".
Genres: adventure, drama, mystery, psychological, supernatural
Themes: folklore, mythology
Episodes: 26
Age Rating: Teen
(Source - ANN)
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I cannot imagine I am the first to have mentioned this anime here before but I can at least open a topic about this anime as I believe it deserves some recognition.
For those who don't know, Mushi are creatures that are neither plant nor animal. They are spirits that haunt our everyday lives and sometimes cause us problems. This is where the Mushi-shi steps in, here known by the name of Ginko. It is his job to track down these troublesome Mushi and rid the victims of them.
This is one of the most beautifully animated anime I have seen in a long while. The forest scenes are such a deeply rich green and the Mushi themselves are very ghostly without being overly spooky (think Princess Mononoke). Although this series is about supernatural events it isn't terrifying in terms of monsters leaping out at you but rather in this way these gentle seeming spirits can affect so many lives in so many different ways.
I wouldn't say I am hooked, I have the whole series and so far I have only watched the first few episodes. It's not like I have to watch several episodes at once, as it is such a slow paced anime. However its a fantastic way to pass the time, and like the X-Files, it should be able to claim some cult status among some of the more mainstream anime. I should also add I have only seen the originals so am unaware what the translated voices sound like.