Smallpox demon (hōsōshin / hōsōgami)

Historical records note that smallpox was introduced into Japan in 735 CE (Shoku Nihongi); thereafter folk belief interpreted outbreaks as caused by spirits and kami, including hōsōshin. Rather than a single cosmogonic origin myth, the hōsōshin concept arises from local and historical responses to smallpox outbreaks in which afflicted households and communities framed the disease as the action of a localized sickness‑spirit or onryō‑like agency.

Textual sources do not give a fixed, standardized bodily description of the smallpox spirit; instead it is treated as a sickness‑spirit or kami. Visual culture contains representations (for example Tsukioka Yoshitoshi’s ukiyo‑e 'Tametomo and Smallpox Demons'), but the provided sources emphasize variability and lack of a canonical anatomy rather than a consistent anthropomorphic form.

Within the tradition the entity is credited with causing smallpox and behaving as an intentional actor whose anger or presence produces illness. It is described as responsive to human ritual behavior—capable of being appeased, praised, or driven off—and as having particular aversions (notably to red objects and to dogs). Some accounts record that, after an outbreak, a household might enshrine the smallpox spirit as a means of securing recovery and preventing further harm, showing it could be transformed into a localized kami through reciprocal ritual.