In a different world, where forests dominate the landscape Ginko a wandering Mushishi travels place to place either seeking out where his services are of use, or being called on by individuals inhabiting scattered villages. Mushishi are masters over the mushi which are the most basic of life, also affecting the world profoundly though only noticed by a select few. The beautiful feel of the setting, attitude of the characters, and often the music all combines to create a great atmosphere with a strong theme of natures power and importance.
However despite all the great, and amazing things about Mushishi, it crumbles at the mention of an actual story. It is episodic, not even in the way that Ghost in the shell had ugly fillers dotted around it, or the way cowboy bebop was 85% filler, but rather all 26 episodes are completely standalone. The main character Ginko is in every episode, and there is one other character who is present in a whopping two episodes but other than that no episode has anything to do with another. Meaning even the last episode ends like the others(as in, he wanders off elsewhere) which could be said to be intentional to show his journey never ends, but if so it's not terribly impactful. Now personally I never view self contained episodes as a good thing, but I would never brand an anime bad simply on that merit. Despite the fact the episode quality doesn't dip low at any particular point the series becomes very redundant.
For example at one point one episode is about someone who's eyesight is failing which wasn't fantastic but wouldn't have been so bad if the following episode wasn't about another child who's hearing had vanished. Furthermore you essentially know the outcome of every episode before it begins. Ginko arrives at a new location and observes something strange, or alternatively, something strange happens and then Ginko arrives. Ginko promptly discovers how to solve the issue and does so, often ending on a melancholy note. Some could like this relaxed redundancy but it really doesn't do much, and though there are a few very beautiful messages, sometimes can go episodes without a good moment.
In it's defense Mushishi never tries to be more than it is, or really tries much at all. It is simply a peek at a beautiful and different world, that is done in all the wrong ways.
The animation of Mushishi is top knotch. The kind of animation I would love to see in a better series. It depicts a world where nature exists over humans, and they are a small, scattered part of it that comes and goes without nature noticing. It is implied the world is undergoing some corruption at humanities hands, and really shows there could be many mysteries in the land. Character animation is not bad, but not the series strong point. Mushi are basic but them and other magical aspects are handled very nicely as well.
Voice acting aside(which is basic but varied) Mushishi is awesome in this department. From the very suitable opening song which really sets the chilled out mood, to the various sounds of nature the audio really sets the mood alongside the great animation. The variety of voice actors is good too, considering we meet many characters during Ginko's journey.
In a word, unimportant. All the kids could be another kid, any adult could be another adult. Really Ginko is the only memorable character, being slightly funny and appearing different, and even he doesn't come close to measuring up to mostly any main character. As I mentioned before only one character is ever in more than one episode, and even then they are only in two, leaving no room for character development(as Ginko is hardly a main character, but rather a means to move things along so he never develops). It's a shame, a more hearty cast could have done wonders for this series, but instead it subsists off of it's animation and feel, as there is literally nothing but the few redeeming qualities about Ginko giving this category any points.
Mushishi is the most dissapointing anime ever, no that does not mean the worst, it simply means it had such unrealized potential. The world it takes place in is really quite interesting, and could have well been the gronds for a fantastic, even if refined and relaxed, story to unfold, but rather it succumbed to redundancy. Yes you should watch Mushishi, any one episode of it, and you will have essentially seen them all. At the end of the day, many people defend Mushishi by saying it's not about Ginko, or the Mushi(which are often turn offs to viewers), but rather it is about the people in the world. Well I find that's hardly the truth because more often than not the only thing that defines them are the Mushi that ail them. It's really about the world and nature, which doesn't need the 26 episodes of self contained episodes to be enjoyed.