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

Three Imperial Regalia and the Kusanagi Sword

In Japanese mythology and imperial tradition, the most important treasures passed down through the ages are the "Three Imperial Regalia (Sanshū no Jingi)". The three sacred treasures that have been said to symbolize the Japanese imperial throne are as follows:

• Yata no Kagami
• Ame no Murakumo no Tsurugi
• Yasakani no Magatama

Of these, the "Ame no Murakumo no Tsurugi" later came to be called the "kusanagi no tsurugi" (Grass-Cutting Sword). This name, derived from a legend of cutting down grass, became established as the most famous sword name in Japanese mythology and history. While often translated as "Grass-Cutting Sword" in English-speaking regions, the Japanese designation "kusanagi-no-tsurugi" has become universally recognized worldwide as is.

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

The first appearance of the Kusanagi Sword is recorded in the Kojiki (compiled in 712) and the Nihon Shoki (compiled in 720).

The story goes as follows. Susanoo no Mikoto, expelled from Takamagahara, descended to Izumo Province (present-day Shimane Prefecture), where he learned of the existence of the fearsome Yamata no Orochi, an eight-headed serpent that devoured a maiden each year. To defeat the monster, Susanoo no Mikoto prepared strong sake to intoxicate the serpent and used the opportunity to sever its eight heads.

When he attempted to cut the serpent's tail, the blade of Susanoo no Mikoto's sword became chipped. Upon inspection, he split open the tail and found a radiant sword within—this was the Ame no Murakumo no Tsurugi. It is said the name derives from the brilliant light the sword emitted, as if appearing from within clouds. Susanoo no Mikoto then 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 by that name through the legend of Yamato Takeru no Mikoto. According to the Kojiki and Nihon Shoki, Yamato Takeru, while conducting campaigns in the eastern provinces, found himself in a dire situation at Sagamu Plain (present-day Shizuoka Prefecture), surrounded by enemies who set fires to trap him.

Cornered by the spreading 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 direction changed, and the flames spread toward his enemies, allowing Yamato Takeru to escape. From this heroic deed, the sword came to be called the "kusanagi no tsurugi" (the sword that cuts down grass).

After completing his campaigns across various regions, Yamato Takeru fell ill from divine retribution at Mount Ibuki (present-day border between Shiga and Gifu Prefectures) and passed away at Nobo Plain in Mie Prefecture. Thereafter, the kusanagi no tsurugi came to be enshrined at Atsuta (present-day Nagoya, Aichi Prefecture).

Historical Events—The Battle of Dan-no-Ura and the Loss of the Sword

The most significant historical event concerning the kusanagi no tsurugi is the Battle of Dan-no-Ura in 1185.

The Battle of Dan-no-Ura was the final confrontation of the Genji-Heike Wars, resulting in the destruction of the Heike clan. At the end of this battle, Ni no Ama (Taira no Tokiko), grandmother of the child Emperor Antoku, entered the sea embracing the young emperor, and it is said that Heike noblewoman attendants who entered the sea with them carried one of the Three Imperial Regalia.

According to the Tale of the Heike, the Yata no Kagami and Yasakani no Magatama were recovered by Genji forces, but the kusanagi no tsurugi is said to have sunk to the bottom of the sea at Dan-no-Ura. Among later historians and Shinto scholars, a debate has continued: "The Kusanagi Sword now enshrined at Atsuta Shrine may not be the authentic one, but rather a different sword (Mikatami no Tsurugi) that had been at Atsuta since before the Battle of Dan-no-Ura."

From the Shinto perspective, the kusanagi no tsurugi is regarded as a "shintai" (sacred object) that should not be seen by human eyes, and it is said that even the Shinto priests of Atsuta Shrine have not seen the actual sword in modern times. This character as an "invisible treasure" adds further mystery to the kusanagi no tsurugi.

Atsuta Shrine—The Dwelling Place of the Kusanagi Sword

Atsuta Shrine, enshrined in Nagoya, Aichi Prefecture, is known as one of Japan's most prestigious major shrines, second only to Ise Shrine in rank. At the core of its worship is the kusanagi no tsurugi as the sacred object.

According to mythological accounts, Atsuta Shrine was founded during the reign of Emperor Keiko (around the 2nd century), though reliable historical records can only be confirmed from the Asuka period onward. The kusanagi no tsurugi is enshrined in the innermost sanctuary, and it is said that neither general worshippers nor even the Shinto priests may directly view it, even during formal religious ceremonies.

Approximately 6.5 million worshippers visit Atsuta Shrine annually, revering it as the guardian deity of the region. The shrine grounds house a museum of treasures where donated swords, armor, and ancient art objects are displayed. While the kusanagi no tsurugi itself is not on display, the museum offers valuable materials that illustrate the relationship between swords and Shintoism.

The Kusanagi Sword and Modern Culture

The kusanagi no tsurugi continues to exert a strong influence on Japanese popular culture in modern times.

The kusanagi no tsurugi is a recurring motif in anime, manga, and games. Kusanagi Kyō, who appears in "The King of Fighters" fighting game series, bears the name of kusanagi, and the aesthetic of blades in contemporary works exemplified by "Demon Slayer" also draws from the mythical imagery of the kusanagi no tsurugi.

The kusanagi no tsurugi is also widely known internationally, and among Western Japanophiles in particular, the name "Kusanagi" has become nearly universal. The name "Kusanagi" is used for swords and weapons in Hollywood films and games, serving as a notable example of the global reach of Japanese sword culture.

The Kusanagi Sword and its Relationship to Japanese Swords

The mythological kusanagi no tsurugi is not a "Japanese sword" in the modern sense. The divine sword mentioned in the Kojiki and Nihon Shoki is believed to have been similar to the "chokuto" (straight sword)—a straight-bladed weapon with either two or one edge—used during the Yayoi to Kofun periods. The modern Japanese sword with a curved blade developed in the mid-Heian period (around the 9th to 10th centuries).

Nevertheless, the kusanagi no tsurugi is regarded as the spiritual source of Japanese sword culture. The notion of divinity dwelling in swords and the spiritual power inherent in blades—these ideas have been continuously passed down from the kusanagi myth and form the basis for modern swordsmiths emphasizing Shinto rituals when forging blades. It can be said to be the origin of the fusion of spirituality and technique in Japanese sword-making.

Conclusion—What the Invisible Sword Tells Us

The kusanagi no tsurugi, with its unique existence as an object never seen by human eyes, occupies the very heart of Japanese mythology, history, and culture. Precisely because it is unseen, its image continues to shine eternally in the imaginations of people.

Through the following three narratives, the kusanagi no tsurugi embodies the origin of Japanese aesthetic consciousness:

• Symbolizing imperial legitimacy as one of the Three Imperial Regalia
• Embodying the courage of the people within the heroic tale of Yamato Takeru
• Serving as a witness to history in the tragedy of Dan-no-Ura

The story of this divine sword exemplifies the origin of Japanese aesthetic consciousness that regards swords not merely as weapons but as crystallizations of culture, faith, and history. Even now in 2026, the mystery enshrined deep within Atsuta Shrine continues to inspire quiet reverence in the hearts of those who visit.