The anime develops themes around nature, mystery / problem solving, and morality. The conflicts typically arise from a man vs. nature imbalance---caused intentionally or unintentionally---and the protagonist must interact with spirits of the land to get to the source of each problem. Many episodes have a sad or mixed ending, but there are heartwarming moments.
One strength of the anime is the way in which nature becomes a central character. The human protagonist is not overbearing, and leaves the viewer to formulate their own opinions. Although the action is infrequent and slow-paced, the mysteries, artwork, and emotional draw are sure to keep the viewer hooked. Mushishi is an excellent anime for people in their 20's.
The show is about a decade old, and some of the artwork---while impressive---lacks the crispness of more recent works. Occasionally the mysteries are predictable.
I strongly recommend this anime to viewers who prefer natural themes, episodic works, slow-paced storytelling, and calming but somber vibes. People looking for action-packed anime or upbeat anime should look elsewhere.
