is a legendary Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese sword

Sword

A sword is a bladed weapon used primarily for cutting or thrusting. The precise definition of the term varies with the historical epoch or the geographical region under consideration...

 and one of three Imperial Regalia of Japan

Imperial Regalia of Japan

The , also known as the Three Sacred Treasures of Japan, consist of the sword Kusanagi , the mirror Yata no Kagami , and the jewel Yasakani no Magatama...

. It was originally called but its name was later changed to the more popular Kusanagi-no-Tsurugi ("Grass Cutting Sword").
The history of the Kusanagi-no-Tsurugi extends into legend. According to Kojiki

Kojiki

is the oldest extant chronicle in Japan, dating from the early 8th century and composed by Ō no Yasumaro at the request of Empress Gemmei. The Kojiki is a collection of myths concerning the origin of the four home islands of Japan, and the Kami...

, the god Susanoo

Susanoo

, also known as is the Shinto god of the sea and storms. He is also considered to be ruler of Yomi.-Myths:In Japanese mythology, Susanoo, the powerful storm of Summer, is the brother of Amaterasu, the goddess of the sun, and of Tsukuyomi, the god of the moon. All three were born from Izanagi, when...

encountered a grieving family of kunitsukami ("gods of the land") headed by in Izumo province

Izumo Province

was an old province of Japan which today consists of the eastern part of Shimane Prefecture. It was sometimes called . The province is in the Chūgoku Region.- History :It was one of the regions of ancient Japan where major political powers arose...

. When Susanoo inquired of Ashinazuchi, he told him that his family was being ravaged by the fearsome Yamata-no-Orochi, an eight-headed serpent of Koshi

Koshi Province

was an ancient province or region of Japan in the area of Echigo, Etchū and Echizen provinces. Also encompassed are Noto and Kaga provinces which were once part of Echizen. It was sometimes called ....

, who had consumed seven of the family's eight daughters and that the creature was coming for his final daughter, .