The Sanchuu (三虫, lit. Three Insects) are parasitic youkai emissaries of Enma-Daiou. The Sanchuu appeared only in the "Nezumi-Otoko and Neko-Musume" story. They live inside every person and tattle to Enma if a person is really wicked. Then a red draft paper is send to a youkai to kill that person. (Source: GeGeGe no Kitarou Wiki)