Korori are disease-spirits of ancient Japanese folklore that were given the task of spreading cholera and in many ways also embodied the dreaded disease, which caused many deaths in Japan. The Korori was envisioned as a demonic yokai that would visit areas stricken with cholera and spread it further. They were also seen as ghouls that would feed on the corpses of those that had succumbed to the fatal plague.
They were part of the Yakubyo Gami family of yokai, who are devoted to spreading sickness and disease, as a result they are also among the most evil and demonic of the yokai (excluding beings such as the oni).