A Hinoshu is a microscopic yokai that resembles a tiny monster in the vague shape of a lumpy boulder with sharp teeth.
It infects a victim's spleen and causes them to develop extreme pain whenever they go out in public, especially if they go near crowds or observe beautiful things.
The belief is that the pain was caused by the Hinoshu becoming excited.
In addition to pain, the spirit's infection causes victims to bruise all over and the only true way to rid oneself of the infection was to consult someone who had previous knowledge of the Hinoshu, who could then help in gaining access to special acupuncture.