Koshi no Mushi is one of the 63 creepy germs written in Harikikigaki, a book of medical knowledge written in 1568 by a unknown resident of Osaka. This tiny malevolent creature was believed to cause human illness during 16th century in Japan.
Koshi-no-mushi is described as small flies with multiple sections. It flies into a host's body and makes its way to the lower back area, where it causes diarrhea, extreme sweating and chest pains. The herbs mokko and kanzo (licorice root) are an effective treatment.