After wreaking havoc in Takamagahara, Susanoo finally incurred the wrath of his older sister, Amaterasu, and was banished.
Susanoo, having been banished from Takamagahara, descended to the land of Torikami on the upper reaches of the Hii River in Izumo Province.
There, he saw a pair of chopsticks floating down the river, leading him to believe that people must live upstream. As he made his way upstream, he encountered an elderly couple weeping with a young woman between them. The elderly couple were the Kunitsukami deities Ashina-zuchi and Tena-zuchi. The young woman’s name was Kushinada-hime.
When Susanoo asked the elderly couple why they were crying, the old man replied, “We had eight daughters. But every year, the Yamata no Orochi would come down from the mountain and devour one of our daughters. It is now the time of year when the Yamata no Orochi will come again, and Kushinada-hime, our last remaining daughter, will also be devoured. That is why we are crying.”
The Yamata no Orochi is a gigantic serpent with eight heads and tails, whose body stretches across eight mountain ridges in the valley. It is said to be a monster with eyes that burn red and a belly that is always covered in festering blood.
Susanoo resolved to slay the great serpent on the condition that he be allowed to marry Kushinada-hime. First, he transformed her into a comb and placed it in his hair.
He then ordered the couple Ashina-zuchi and his wife to brew strong sake, build a fence, set up eight gates, and place sake vessels filled with the sake at each gate.
As they waited with their preparations complete, the great serpent finally arrived. The great serpent plunged its eight heads into the eight sake vessels and drank them dry, then passed out drunk and fell asleep. Susanoo, who had been waiting for this moment, sliced the serpent to pieces with his sword, and the Hii River was dyed red with the spatter of blood.
He began to slice into its body. When the blade reached the serpent’s tail and cut it open, a magnificent sword emerged from within. He presented this sword to Amaterasu. This sword would later be known as the Kusanagi Sword and come to be regarded as one of the Three Sacred Treasures of the Imperial Household.