Hinamizawa (in Japanese: 雛見沢) is a dangerous little Japanese town. This village is known for being a carrier of an unusual disease called Hinamizawa syndrome, which was originally mistaken for the curse of their god Oyashiro-sama. Those who were infected with this disease became paranoid and insane, which then often ended with them killing themselves by slitting their throats.

The Hinamizawa Syndrome (雛見沢症候群, Hinamizawa Shōkōgun) is a fictional organic brain disease of uncertain etiology, endemic to the residents of Hinamizawa. It appears to be caused by a type of parasite which can only be recovered from living tissue. How inhabitants and visitors acquire it remains unknown. The parasite appears quiescent until triggered— usually when the infected leaves the region or when the infected undergoes significant physiological or psychological stress. The signs and symptoms of the Syndrome include the development of anxiety and paranoia accompanied by delusions which can lead the sufferer to commit seemingly unprovoked violent acts including suicide and murder, and the sensation of insects crawling under their skin, a real-life symptom known as formication. This leads to a classic sign of clawing at the skin, especially over the involved lymph nodes of the throat. Victims in the end-stages may claw out their own throat and die from the resulting blood loss.

The Watanagashi Festival (綿流し祭, Cotton Drifting Festival) is the largest celebration of the year for the rural village of Hinamizawa. It takes place on the third Sunday of June and gives thanks and praise to the village's guardian god, Oyashiro-sama. Two versions have been practiced through the ages.