Mushi are some sort of proto-life form. Ginko, a traveller, is a Mushishi: someone knowledgable in the ways of the Mushi. He gets called in when humans and Mushi brush past eachother, sometimes with undesirable results.
There is the boy whose drawings come to life, or the girl who lost her eyesight because she kept her second eyelid shut for too long, or the village where people can't hear anything in the winter...
Ginko is the eternal outsider: he attracts mushi, and so can't stay in one place for too long. People have a problem, he comes along and tries to fix it, and sometimes people and mushi go their separate ways after the problem has been resolved. By collecting rare mushi-related items and selling these to some collectors, Ginko gets by. He always tries to preserve the balance between humans and mushi -- in his view, the mushi simply do what is in their nature, and you shouldn't blame them if they cross paths with humans and this is in some way detrimental to the humans.
The series is incredibly episodic: every episode, Ginko solves a mushi-related case. There is very little backstory (we only get two disjunct episodes about Ginko's past), and no overall plot whatsoever. The stories themselves are (almost) always beautiful and intriguing. There were only two episodes that I felt were a little below the level of the others. Some stories are spaced over multiple years: in the first part Ginko visits a village, and then returns after some time has passed in the second part.
The stories have a bittersweet feel to them: if the episode ends on a happy note, there is some cause for sadness or melancholy. If the episode ends on a sad note, there is some cause of hope and happiness. This is really hard to pull off consistently, but the writers nailed it precisely.
The episodes are really slow-paced. It fits with the atmosphere and gives enough time for explanations and expositions. There is very little action, and yet I was completely captivated by each and every episode.
The world of Mushishi is a weird one. In outlook, it seems to be set in the classical period: people were kimono and live in small villages. Villagers grow rice to feed themselves, and there are very few 'professionals' around. There's the doctor and the weaponsmith, but that's about it.
On the other hand, it feels quite modern: women can travel alone without bad consequences, people frequently travel large distances, and food and commerce are considered very normal. Ginko himself wears something that looks like a leisure shirt and jeans, while everyone else wears kimono. Perhaps this serves to emphasize Ginko's status as an outsider, and adds to the melancholic and nostalgic feeling of the series.
Visually, the series is stunning. The backgrounds are really detailed and lush. This being set in the backwaters of rural Japan, we get incredibly detailed renderings of mountain forests.
Animation-wise, there is not much action. Sometimes a mushi moves a lot (in which case it's animated quite nicely), but most of the time the animation follows the slow pace of the storytelling.
The character designs are all quite similar -- it is as if the character designer could draw only one type of face. This doesn't really distract from the episodes, as there are no recurring characters (except for Ginko).
The music is really good. The melodies really fit with the atmosphere of the series. The voice acting is good, if nothing special.
- Excellent storytelling;
- Excellent atmosphere;
- Good visuals;
- Excellent music.
- Little variation in character designs.
In conclusion, this is the best series you haven't seen -- and you really, really should. I will give it a 9.