To piece togther the Japanese legends from various sources (
1,
2);
"Izanagi and Izanami stood on the floating bridge of Heaven and held counsel together, saying, “Is there not a country beneath?” Thereupon they thrust down the jewel-spear of Heaven and, groping about therewith, found the ocean. The brine which dripped from the point of the spear coagulated and became an island which received the name of Ono-goro-jima. The two deities thereupon descended and dwelt in this island.
Izanagi no Mikoto and Izanami no Mikoto consulted together saying, “We have now produced the great-eight-island country, with the mountains, rivers, herbs, and trees. Why should we not produce someone who shall be lord of the universe? They then together produced the Sun Goddess, who was called [Amaterasu]....The resplendent luster of this child shone throughout all the six quarters. Therefore the two deities rejoiced saying, “We have had many children, but none of them have been equal to this wondrous infant. She ought not to be kept long in this land, but we ought of our own accord to send her at once to Heaven [...]
[Izanagi and Izanami’s] next child was Susa no o no Mikoto….This god had a fierce temper and was given to cruel acts."
So, as punishment for being so wild, Susa-no-o was cast out of Heaven and sent to wander Japan. The sinister Orochi, an eight-headed dragon, is said to have dominated the Izumo province in Japan, and to have demanded maiden sacrifices. When Susa no o came upon this area, he met an old couple. They told him that they had already sacrificed seven daughters to the dragon, and that the eighth was to be sacrificed next. The daughter in question here was named Kushinada, and since she was a very beautiful and kind young girl that Susa no o fell deeply in love with, he told the couple that he would rescue Kushinada if he was allowed to marry her. The couple agreed at once.
Susa-no-o turned Kushinada into a comb and put her in his hair. He then put out eight barrels of sake, which the dragon drank with relish, making it fall asleep, and Susa no o proceeded to cut off all of Orochi's heads. He found the sword, Ame-no-Murakumo (later named Kusanagi), in one of the serpent's many tails. In some versions, Kusanagi is called Kusanagi-no-Tsurugi, 'The Grass-Cutting Sword', and this sword was given to Amaterasu, Susa-no-o's sister, the Sun Goddess, as a gift of reconciliation.

And guess what? GS gets a mention in Wikipedia's Orochi page;
"In Golden Sun: The Lost Age, the Orochi is portrayed as an invincible Chinese dragon that has to be weakened by light orbs before it can be killed. The story is nearly identical except that Kushinada is not turned into a comb and the dragon was killed by the protagonists instead of Susa-no-o. In addition, after defeating the boss, a sword called the "Cloud Brand" can be found near the dragon's tail, a reference to the Kusanagi. "
Susa and Kushinada the subjects of the odd bit of fanart - Feizhi and Hama too:
