Sword〈Inscribed Choso Nekori Nyudo No Toru〉

Sword, Signed "Nagasone Okisato Nyūdō Kotetsu" — A Masterpiece by the "Yokozuna of New Swords"

Among the countless Japanese swords forged across more than a thousand years of tradition, only a select few earn the rare designation of Important Cultural Property. The katana inscribed "Nagasone Okisato Nyūdō Kotetsu," preserved in Okayama Prefecture, is one such treasure. Forged in 1674 (Enpō 2) by the celebrated swordsmith known simply as Kotetsu, this blade represents the pinnacle of the early Edo period's "new sword" (shintō) tradition. Its remarkable cutting ability, refined craftsmanship, and the distinguished history of having been handed down through the Okudaira daimyo family make it a masterwork that captivates collectors, scholars, and admirers of Japanese culture from around the world.

The Swordsmith Behind the Legend: Nagasone Kotetsu

The maker of this blade, Nagasone Okisato — better known by his Buddhist name Kotetsu — is one of the most celebrated swordsmiths in Japanese history. Born around 1605, he initially earned his livelihood as an armorer (kacchūshi) in Echizen Province, in present-day Fukui Prefecture. Around the age of fifty, he relocated to Edo (modern-day Tokyo) and remarkably transformed himself into a master swordsmith. Although his career as a maker of blades lasted only about twenty years until his death in 1678, his work redefined what was possible in the new sword era.

Kotetsu's blades were so renowned for their cutting ability that the Edo-period sword evaluation manual Kaihō Kenjaku (1797) ranked him in the highest class, "Saijō Ō-wazamono" — the supreme cutting grade. Together with Horikawa Kunihiro of Yamashiro, he was praised as one of the two "yokozuna" of the new sword period. Demand for his work was so intense, even during his own lifetime, that counterfeit blades flooded the market — giving rise to the famous saying among Japanese sword connoisseurs: "When you see a Kotetsu, assume it is a fake."

The Three Eras of the Kotetsu Signature

One of the most distinctive features of Kotetsu's career is the evolution of his signature. The character pronounced "kotetsu" was written in three different forms across his working life. His earliest works bore the inscription 古鉄, literally "old iron," reflecting his use of recycled iron such as old nails. He later adopted the character 虎徹, written with a distinctive flourish on the final stroke and known among connoisseurs as "Hanetora." In his final and most refined period, he used the simplified form 乕徹, called "Hakotora."

This sword, signed with the Hakotora form, dates from the late phase of Kotetsu's career, when his craftsmanship is widely considered to have reached its highest expression. Specialists agree that the works produced during the Hakotora years represent the absolute summit of his artistry, and every Kotetsu blade designated as a national Important Cultural Property comes from this final, masterful period.

Why This Sword Was Designated an Important Cultural Property

This katana was officially designated an Important Cultural Property by the Japanese government on February 18, 1949. The reasoning behind its designation reflects multiple layers of artistic, technical, and historical significance.

First, the blade is a fully signed and dated work from Kotetsu's most accomplished period. With a cutting edge length of 76.3 centimeters and a curvature of 2.1 centimeters, the sword displays a substantial and elegant profile. The forging is executed at the highest level, exhibiting a tightly forged ji-hada (steel grain pattern) and a brilliantly tempered hamon (the cloud-like temper line) characteristic of Kotetsu's mature style.

Second, the sword preserves an unaltered tang (nakago) with a single mekugi-ana (peg hole), and the original signature remains intact. In a body of work plagued by countless counterfeits, an authenticated and signed Hakotora-period Kotetsu of this quality is exceedingly rare.

Third, the blade's documented provenance through the Okudaira family — a prominent daimyo lineage with deep connections to the Tokugawa shogunate — adds significant historical weight. Such pieces, treasured as heirlooms of warrior families, embody not only the swordsmith's craftsmanship but also the cultural prestige attached to fine blades in samurai society.

Artistic Highlights and Points of Appreciation

The Form (Sugata)

Unlike many swords of the Kanbun-era new sword style, which tend to be straight with shallow curvature, this blade reflects an awareness of the more graceful curvature seen in classical Kamakura-period tachi. The result is a sword that combines the refined silhouette of older masterpieces with the cutting prowess that made Kotetsu famous. The 2.1 cm sori suggests the smith deliberately departed from the conventions of his era, perhaps in response to a special commission.

The Hamon (Temper Line)

The temper line is one of the most expressive features of any Japanese sword, and Kotetsu's late-period work is celebrated for what is known as the juzuba — a "rosary bead" pattern of rounded, evenly spaced undulations resembling prayer beads. This pattern, characteristic of his Hakotora years, is rendered here with bright, clear nie crystals (martensite particles visible to the naked eye) that lend the edge a luminous, three-dimensional quality.

The Ji-hada (Steel Grain)

Kotetsu's training as an armorer gave him an exceptional command of steel, and his ji-hada is admired for its tightness, depth, and clarity. Subtle activities such as kinsuji (golden lines) and chikei (dark lines within the steel) animate the surface, rewarding extended viewing under angled light.

The Inscription

The signature, cut on the omote (front) face of the tang, reads "Nagasone Okisato Nyūdō Kotetsu" — incorporating the smith's lay name Okisato, his Buddhist title Nyūdō indicating his ordination as a monk, and the Hakotora form of his art name. The fact that the signature is on the omote face is itself notable: it indicates the blade was originally intended to be worn as a tachi (slung edge-down), an unusual choice for the late seventeenth century.

The Legacy of the Okudaira Family

The Okudaira family, through whom this sword was transmitted, was a distinguished daimyo lineage with strong Tokugawa connections. Their possession of this Kotetsu reflects both their refined taste and the high regard in which Kotetsu's blades were held among the upper ranks of warrior society. Throughout the Edo period, owning a documented Kotetsu was a mark of considerable status, with such swords frequently exchanged as ceremonial gifts among the most powerful houses of the realm.

Visiting Information and Where to Encounter Kotetsu's Work

This particular sword is held in private ownership in Okayama Prefecture and is therefore not on regular public display. However, on rare occasions it has been shown to the public — for example, during the 2018 special exhibition "Kotetsu and the Great Swords of the Bakumatsu and Meiji Restoration" held at the Okayama Prefectural Museum. International visitors interested in seeing this masterpiece should monitor announcements from major Japanese sword exhibitions.

For travelers eager to experience Kotetsu's craftsmanship in person, several institutions across Japan regularly display his works. The Tokyo National Museum, the Japanese Sword Museum (Tōken Hakubutsukan) in Tokyo, the Kyoto National Museum, the Akisui Museum in Toyama, and the Kashiwabara Museum of Art in Yamaguchi all hold authenticated Kotetsu blades. Edo-Tokyo Museum has also displayed his rare naginata.

Exploring the Surrounding Region: Okayama

Okayama Prefecture, where this sword resides, is one of Japan's most rewarding cultural destinations. Visitors can explore Okayama Castle, with its striking black exterior that earned it the nickname "Crow Castle," and stroll through Kōrakuen Garden, ranked among the three great gardens of Japan. The historic town of Kurashiki, with its preserved Edo-period canal district, offers a window into the merchant culture of the period when this very sword was treasured by the Okudaira family.

For those drawn to Japanese sword culture, the nearby Bizen-Osafune region — a short journey from Okayama City — was historically the heartland of Japan's most prolific sword-making tradition. The Bizen Osafune Japanese Sword Museum allows visitors to witness traditional forging demonstrations and view masterworks from the Bizen tradition that influenced generations of swordsmiths, including Kotetsu himself.