Manga by author Urushibara Yuki

Some live in the deep darkness behind your eyelids. Some eat silence. Some thoughtlessly kill. Some simply drive men mad. Shortly after life emerged from the primordial ooze, these strange creatures, called "mushi", came into being. Ginko, a wanderer with a sardonic smile, is a "mushishi" one who has the knowledge and the skill, to help people get rid of their various mushi related problems.