Recorded in the Kojiki (record of ancient matters), and the Nihon Shoki (The Chronicle of Japan) the oldest existing written records of Japanese history, is the story of the imperial regalia sword of the Japanese Emperor. Written in the eighth century, most of its early records are considered to be mythical. It is written that the storm God Susanoo no Mikoto slayed an eight-headed and eight-tailed giant serpent called Yamata-no-Orochi whilst saving Princess Kushinada-hime. Susanoo plied the serpent with sake until it was drunk and killed it. Then, as he cut open its tails, he found a sword (known as Ama no Murakumo no Tsurugi - The Heavenly Gathering of Clouds Sword). He later presented it to his sister Amaterasu Omi Kami the Sun Goddess.
Amaterasu later gave the Ama no Murakumo no Tsurugi to her grandson Ninigi, when he came down to Earth. Ninigi in turn gave it to his grandson Emperor Jimmu (The first emperor of Japan) along with a mirror and jewel (magatama). These three treasures came to be known as the Imperial Regalia: symbols of imperial authority and legitimacy, providing the link between the imperial family and their divine ancestry. According to The Nihon shoki, Ise shrine was established by Yamato-hime no Mikoto, the daughter of the legendary Emperor Suinin (reigned ca 29 B.C. to 70 A.D.), as a residing place for the Imperial regalia. She later loaned the sword to her nephew Prince Yamato Takeru no Mikoto when he was leaving to subjugate the Ainu.
A famous account of Prince Yamato Takeru no Mikoto and the Ama no Murakumo no Tsurugi came when he was surrounded by the Ainu whilst hiding in the long grass. The Ainu set fire to the grass in order to flush him out or kill him. Prince Yamato Takeru used the sword to cut down the grass and escaped. Accounts of this event vary slightly with another version, which implies that the sword had magical powers and flew out of the scabbard by itself to cut down the long grass - thus saving the young Prince. From this time onward the sword was to be known as the Kusanagi no Tsurugi (The Grass Cutting Sword).
This sword was to be the subject of more controversy in 1185 at the Battle of Dan-no-Ura, the culmination of the Gempei wars between the Taira and Minamoto clans. The three items of the imperial regalia were thrown into the sea when the child Emperor Antoku drowned in the arms of Nii Dono, wife of Taira Kiyomori. Legend has it that the Jewel and Mirror floated to the surface and were saved but the sword was lost. Later accounts report that this was not the actual Kusanagi no Tsurugi, but a copy and that the original still resides in Atsuta Jingu in Nagoya to this day.