Kusanagi (草薙 Grasscutter) is a legendary Japanese sword, as important to Japan's history as Excalibur is of Britain's. It is a powerful sword like the Katana.
The history of this sword extends into legend when the Japanese god, Susano-O-No-Mikoto encountered a grieving family headed by Ashi-Na-Zuchi. Upon inquiry, the elder told that his family was ravaged by the fearsome 8-headed serpent of Koshi who consumed seven of the family's eight daughters and the creature was coming for his final daughter, Kushi-Nada-Hime. Susano proceeded forward to investigate the creature, and after an abortive encounter he returned with a plan to defeat it. In return, he asked for Kushi-Nada-Hime's hand in marriage which was agreed. Transforming her temporarily into a comb to have her company during the battle, he detailed his plan.
He instructed the preparation of 8 vats of rice-beer to be put on individual platforms positioned behind a fence with 8 gates. The monster took the bait and put each of its heads through each of the gates. With the necessary distraction provided, Susano attacked and slew the beast. He decapitated each of the heads and then proceeded to the tails. In the fourth tails, he discovered a great sword inside the body with Susan-o which he called Murakakumo-No-Tsurugi (Sword-of-the-village-of-the-clustering-clouds) which he presented to the god, Amaterasu to settle an old grievance.
Generations later in the reign of the 12th emperor, Keiko, the sword was given to the great warrior, Yamato-Dake as part of a pair of gifts given by his aunt, Yamato-Hime, to protect his nephew in peril.
These gifts came in handy when Yamato-Dake was lured onto an open grassland during a hunting expedition by a treacherous Daimyo. The lord, had fiery arrows fired to ignite the grass to trap Yamato-Dake in the field and have him burn to death and killed the warrior's horse to prevent his escape. Desperately, Yamato-Dake used Murakakumo-No-Tsurugi to cut back the grass to remove fuel from the fire, but in doing so, he discovered that the sword enabled him to control the wind around to make it move in the direction he swung. Taking advantage of the magic, Yamato-Dake used his other gift, fire strikers, to enlarge the fire in the direction of the lord and his men and used the winds controlled by the sword to sweep the blaze toward them to kill them. In triumph, Yamato-Dake renamed Murakakumo-No-Tsurugi as Kusanagi (Grasscutter) to commemorate his narrow escape and victory.
Eventually, Yamato-Dake married and fell in battle with a monster after ignoring his wife's advice to take Kusanagi with him.
Eventually, the sword came into the possession of the emperor until the Battle of Dannoura, a naval battle that ended in the defeat of the forces of the child Emperor, Antoku at the hands of Minomoto Yoshitsune. Upon hearing of the defeat, the emperor's grandmother led the Emporer and his entourage to commit suicide in the waters of the strait along with three important artifacts which included Kusanagi. Although the enemy managed to stop a handful of them and recovered two of the three items of the Emperor, Kusanagi was never found.
The 10th Emporer, Sujin, ordered the fashioning of a replica of Kusanagi and was placed at the Temple of Atsuta.
