This article is incomplete. Reason: Description section must be added; story must be rewritten into sections of Background and Ōkami to follow a chronological order. Please feel free to add the missing information and fill in the missing sections. PLEASE DO NOT ADD SPECULATION OR IRRELEVANT INFORMATION.
The 8 Purification Sake (「八塩折之酒」?; Yashiori-no-sake) is a special holy type of sake made from spring water from Hitoshio Spring in Agata Forest. It was used by Nagi 100 years ago to intoxicate Orochi to leave it vulnerable to attack. It is the only known substance capable of that. It is usually drunk during the Kamiki Festival which is held every year.
8 Purification Sake is first introduced when Amaterasu and Issun help Kushi gather holy water for the sake from Hitoshio Spring in Agata Forest (and later protect her from imps with Susano). The holy properties of the very water are shown here, as it can generate a protective barrier capable of stopping common Imps. Kushi then takes the water back to Kamiki Village and matures it in the large sake barrel in her house. However, on the night of the annual festival, Susano drinks all the sake and hides in his house. The newly-returned Orochi then selects Kushi as its ritual sacrifice. Kushi is forced to go to the Moon Cave where Orochi waits, but then reveals she has made a less-powerful version of the 8 Purification Sake with some of the holy water, Thunder Brew. She drops it when Orochi takes her, but it is later found by Amatersu and Issun in the Calcified Cavern in the depths of the Moon Cave. Amaterasu later manages to make Orochi drink the Thunder Brew, but because of its weaker powers, it does not affect the serpent and the bottle falls to the ground. However, at that moment, Susano appears, ready to fight Orochi. It is then shown that the open bottle of sake was flowing into grooves on the floor. Susano's courage awakens the power in the sake and it become proper 8 Purification Sake. Amaterasu then uses it to defeat Orochi.
8 Purification Sake later appears in Kamiki Village when Amaterasu travels back in time. This time it was created by Nami, Kushi's ancestor. Amaterasu uses it to fight True Orochi.
Spoilers end here.
The 8 Purification Sake inexplicably appears in the moat surrounding True Orochi in the rematch against the demon on the Ark of Yamato. The sake's existence on the ark may be based on the ark's ability to simulate the environment of different given circumstances, thanks to Moon Tribe technology.