Mushishi Tokubetsu-hen: Suzu no Shizuku

The anime adaptation of the final Mushishi manga arc. Ginko stumbles upon a young girl in a mountain with branches and leaves growing out of her body. He later realises that she is the lord of that mountain but finds it strange that a human like her was chosen as the lord. He later meets her older brother who has continued to search for her ever since she disappeared while she was accompanying him on a stormy day. The story is about that girl, Kaya, and how she is torn between continuing her duty as a mushi lord and returning back to her loving human family.
(Source: Anime News Network)