Kusanagi-no-Tsurugi: Japan's Mythological Grass-Cutting Sword and the Three Imperial Treasures

The Three Sacred Treasures and the Kusanagi Sword

In Japanese mythology and imperial tradition, the most important treasure passed down through generations is the "Three Sacred Treasures" (Sanshū no Jingi). The Yata Mirror, the Ame no Murakumo no Tsurugi, and the Yata no Magatama—these three have been regarded as the sacred treasures symbolizing the Japanese throne.

Of these, the "Ame no Murakumo no Tsurugi" later became known as the "Kusanagi no Tsurugi" (Grass-Cutting Sword). This name, derived from the legend of cutting down grass, has become the most well-known sword name in Japanese mythology and history. In English-speaking regions, it is sometimes translated as "Grass-Cutting Sword," but the Japanese term "kusanagi-no-tsurugi" is itself widely used globally.

Mythological Origins—Yamata no Orochi and the Slaying of the Eight-Branched Serpent

The first appearance of the Kusanagi no Tsurugi is recorded in the Kojiki (712 CE) and the Nihon Shoki (720 CE).

The story goes as follows. Susanoo no Mikoto, banished from Takamagahara, descended into Izumo (present-day Shimane Prefecture), where he learned of the terrifying Yamata no Orochi, an eight-branched serpent that consumed a maiden each year. To vanquish the monster, Susanoo prepared strong sake to intoxicate the serpent, then seized the opportunity to sever its eight heads.

As Susanoo attempted to cut the serpent's tail, the blade of his sword became chipped. Suspecting something amiss, he split the tail open, and from within emerged a gleaming sword—the Ame no Murakumo no Tsurugi. The name is said to have derived from the light the sword emitted, as though appearing from within clouds. Susanoo presented this divine sword to his sister goddess, Amaterasu Ōmikami.

Yamato Takeru and the Naming of "Kusanagi"

The Kusanagi no Tsurugi came to be called "Kusanagi" (Grass-Cutting) from the legend of Yamato Takeru no Mikoto. According to the Kojiki and Nihon Shoki, while campaigning in the eastern provinces, Yamato Takeru found himself trapped by enemies who set the grass fields ablaze in the region of Sagami (present-day Shizuoka Prefecture).

Cornered by the expanding flames, Yamato Takeru drew the Ame no Murakumo no Tsurugi he had received from his aunt, Yamato Hime no Mikoto, and cut down the surrounding grass. The wind shifted, and the flames turned toward his enemies, allowing Yamato Takeru to escape. This feat gave the sword its name, "Kusanagi no Tsurugi" (the Grass-Cutting Sword).

After completing his campaigns throughout the land, Yamato Takeru began his return journey, but on Mount Ibuki (now on the border between Shiga and Gifu Prefectures) he was struck by the curse of a god, fell ill, and died in Nobo (present-day Mie Prefecture). The Kusanagi no Tsurugi was subsequently enshrined in Atsuta (present-day Nagoya, Aichi Prefecture).

Historical Events—Dan no Ura and the Loss of the Sword

The greatest historical incident involving the Kusanagi no Tsurugi was the Battle of Dan no Ura in 1185.

At Dan no Ura, the final decisive battle of the Genpei War, the Heike clan was destroyed. As the battle ended, the grandmother of the young Emperor Antoku, Nii no Ama (Taira no Tokiko), entered the sea while holding the young emperor, and the Heike noblewomen who followed her into the waters are said to have carried one of the Three Sacred Treasures.

According to the Heike Monogatari, the Yata Mirror and Yata no Magatama were recovered by Minamoto forces, but the Kusanagi no Tsurugi is said to have sunk to the bottom of the Dan no Ura strait. Among later historians and Shinto scholars, the debate continues: "The sword currently enshrined at Atsuta Shrine may not be the original Kusanagi, but rather a different sword (Migokatasumi no Tsurugi) that had been at Atsuta since before Dan no Ura."

From the Shinto perspective, the Kusanagi no Tsurugi is a "shintai" (sacred object) that is not shown to human eyes, and even in modern times, the priests of Atsuta Shrine are said not to have seen the actual sword. This character as an "unseen treasure" has given the Kusanagi no Tsurugi further mystique.

Atsuta Shrine—The Dwelling Place of the Kusanagi

Atsuta Shrine, located in Nagoya, Aichi Prefecture, is known as one of Japan's premier shrines, second only to Ise Grand Shrine in status. At the heart of its worship lies the Kusanagi no Tsurugi as its sacred object.

The founding of Atsuta Shrine is traditionally placed in the reign of Emperor Keikō (around the 2nd century) according to mythological accounts, though reliable historical records date from the Asuka period onward. The Kusanagi no Tsurugi is enshrined in the innermost sanctum of the main hall, and it is said that not even the shrine's priests are permitted to view it directly, much less ordinary worshippers.

Approximately 6.5 million pilgrims visit Atsuta Shrine annually, venerating it as a protector deity of the region. Within the shrine grounds stands a treasure museum displaying donated swords, armor, and ancient art. Although the Kusanagi no Tsurugi itself is not on display, the museum houses valuable materials illustrating the relationship between swords and Shinto.

The Kusanagi and Modern Culture

The Kusanagi continues to exert a powerful influence on Japanese popular culture today.

In anime, manga, and video games, the Kusanagi is a recurring motif. "Kusanagi Kyo," a character in the fighting game series "The King of Fighters," bears the Kusanagi name, and the blade aesthetics of contemporary works like "Demon Slayer" are likewise connected to the mythological imagery of the Kusanagi.

Furthermore, the Kusanagi is widely known internationally, and the name "Kusanagi" has become virtually a universal term among Japanophiles in the West. The name "Kusanagi" is frequently used in Hollywood films and video games for naming swords and weapons.

The Kusanagi and the Japanese Sword

The mythological Kusanagi is not a "Japanese sword" in the modern sense. The divine sword described in the Kojiki and Nihon Shoki is believed to have been close to the "chokutō" (straight sword)—a straight, double-edged or single-edged blade—used during the Yayoi and Kofun periods. The modern "Japanese sword" with its characteristic curved blade emerged during the mid-Heian period (around the 9th to 10th centuries).

Nevertheless, the Kusanagi is positioned as the spiritual source of Japanese sword culture. The divinity that resides in the sword, the spiritual power possessed by blades—these concepts have been continuously inherited from the mythology of the Kusanagi and remain the foundation for the emphasis on Shinto ritual when modern swordsmiths forge their blades.

Conclusion—What the Invisible Sword Speaks

The Kusanagi no Tsurugi, though never seen by human eyes, occupies the very heart of Japanese mythology, history, and culture. Because it is unseen, its form shines eternally in the imagination of people.

As one of the Three Sacred Treasures symbolizing imperial legitimacy, embodying the courage of the people in the heroic tales of Yamato Takeru, and serving as a witness to history at the tragedy of Dan no Ura—the story of the Kusanagi no Tsurugi may be said to be the origin of Japan's aesthetic sensibility, one that regards the sword not merely as a weapon, but as the crystallization of culture, faith, and history. Even now in 2026, the mystery that dwells deep within Atsuta Shrine continues to evoke quiet reverence in the hearts of pilgrims who visit.