early 1800s
Water Purification is a tradition of Kurodoro.
Water Purification is a private ritual conducted by the village's shrine maiden (Myouka) on an individual basis. Every time a new person arrives to the village, or whenever a child within the village grows to a certain age, the shrine maiden calls them inside the shrine and has them drink a special concoction. This brew causes the imbiber to suffer from intense fever symptoms that tie them to the bed for a week on average. The imbiber goes through a life-threatening traumatic experience that practically disables them for the duration of the fever and causes potentially irrepairable damage to their organism. The conclusion of the fever decides the outcome of the ritual. If the imbiber perishes from the illness, the shrine maiden proclaims them a demon in disguise, effectively unmasking and eradicating them with the help of the concoction. If the imbiber endures through the fever and survives, the shrine maiden proclaims them a pure human who has proven their humanity and is not to be subjected to the ritual again.
Water Purification has a counterpart in the form of the Air Purification.