Watanagashi Festival

The Watanagashi Festival (綿流し祭) is an annual festival in Hinamizawa and serves as a fixed point in every story of. The festival, while outwardly innocent, coincides with a series of gruesome murders that occur in Hinamizawa: the dam construction site murder, the dam supporters' accident, the priest's death, and the murder of the housewife. It's purpose as a fixed point in Higurashi's story arcs makes the Festival analogous to Beatrice's letter in.

History
The festival began centuries previously as a time to cast off the sins of the villagers via human sacrifice. Said sacrifice would be publicly tortured using the tools in the Saiguden in a very specific process (including putting nails through every joint in every finger of the victim) before finally being killed by the priest or miko, who gouges out the victim's stomach and intestines with a large, hoe-like dissection tool following an intricate dance. The corpse and its severed intestines would then be thrown into the river to wash away, symbolizing the "drifting away" of the people's sins with the victim's innards. In modern times, however, the original Watanagashi Festival became viewed as too violent and cruel to be practiced. Instead, the villagers began practicing the modern Watanagashi known as the Cotton-Drifting Festival. Everyone in the village would contribute old coats and furniture to be gutted for their cotton. Said cotton would then be sewn into a large futon which would take the place of the traditional human sacrifice. On the night where the human is traditionally subjected to intestine gouging, the priest or miko would perform a dance and instead use the hoe to cut the futon and gouge out the cotton in place of intestines. Each villager then takes a small amount of this cotton and sets it adrift on the river to absorb and "drift away" the sins and sadness of the villagers. Despite the Festival's changed nature, the torture tools used in the original Watanagashi still exist within the Saiguden.

Hanyuu Furude was originally sacrificed by her daughter Ouka Furude as part of the traditional Watangashi Festival. Her unique horns led the villagers to call her a demon unworthy of life. As such, Hanyuu wished to die and carry away the sins of the villagers. However, her sacrifice led to her becoming a godlike figure commonly known as Oyashiro.

Trivia

 * The word wata in Watanagashi is typically read using 綿, which means "cotton". However, wata can also be read using 腸, which means "guts", "intestines", or more simply, "organs". By reading wata this way, the Watanagashi Festival is given the more gruesome translation of "organ-drifting festival". This translation was the original meaning of the name "Watanagashi".
 * Due to the strong "ritual impurity" taboos regarding death in Japanese religion and culture, the concept of human sacrifice in a Shinto ritual is not only violent and cruel, but also blasphemous and profane, similar to Western depictions of Satanism.