Tachi〈Memorial Chikushu Juza (Esetsu Samonji)〉

Kōsetsu Samonji: The Legendary National Treasure Tachi

Among Japan's vast collection of designated National Treasure swords, few carry as rich a story as the Kōsetsu Samonji (江雪左文字). This magnificent tachi — a type of long, curved Japanese sword worn edge-downward — was forged in the early Nanboku-chō period (14th century) by the renowned swordsmith known as Ō-Sa, the founder of the Samonji school in Chikuzen Province (present-day northwestern Fukuoka Prefecture). Today, this extraordinary blade is preserved at the Fukuyama Museum of Art in Hiroshima Prefecture, where visitors can witness firsthand the artistry that has captivated warriors, shoguns, and collectors for nearly seven centuries.

The Master Swordsmith: Samonji (Ō-Sa)

The Kōsetsu Samonji was crafted by the first-generation Samonji, whose full name was Minamoto Saemon Saburō. He signed his blades simply with the character "Sa" (左), an abbreviation of his given name, and this distinctive signature gave rise to the school name "Samonji" — literally meaning "the character Sa." He is also widely known by his honorific nickname Ō-Sa, meaning "The Great Sa," a testament to his extraordinary skill.

Samonji is traditionally counted among the Masamune Jittetsu — the "Ten Great Students of Masamune" — the legendary group of master swordsmiths who studied under Gorō Nyūdō Masamune, widely regarded as Japan's greatest swordmaker. Whether Samonji traveled from distant Chikuzen to Kamakura to study directly under Masamune remains a subject of scholarly debate, but the influence of the Sōshū tradition is unmistakable in his work. Samonji revolutionized the swordmaking tradition of Kyushu, departing from the subdued, straight-tempered blades typical of the region and instead adopting the brilliant, richly patterned style characterized by strong nie (visible crystalline structures) and vivid hamon (temper lines).

While Samonji was celebrated as a master of tantō (short blades), his surviving tachi are exceptionally rare. The Kōsetsu Samonji stands as one of only two known signed tachi by this smith — making it an irreplaceable treasure in the history of Japanese swordmaking.

Why It Was Designated a National Treasure

The Kōsetsu Samonji was designated a National Treasure of Japan on June 9, 1951, under the official name "Tachi, signed Chikushū-jū Sa (Kōsetsu Samonji)," with the accompanying uchigata-na koshirae (sword mounting) listed as an appended item. Several factors contributed to this prestigious designation:

• Extreme rarity: As one of only two surviving signed tachi by the first-generation Samonji — a master renowned primarily for tantō — this blade represents an extraordinarily rare example of the smith's work in a longer format.
• Exceptional craftsmanship: The blade exhibits all the hallmarks of Samonji's finest work: tightly forged ko-itame (small wood-grain) steel, thick ji-nie (crystalline particles on the surface), prominent chikei (dark lines in the steel), and a brilliant, deeply complex hamon with strong nie and a brightly gleaming nioiguchi (boundary of the temper line).
• Historical significance: The sword's provenance reads like a chronicle of Japanese history, passing through the hands of some of the most influential figures of the Sengoku and Edo periods.
• Outstanding preservation: Despite being shortened (suriage) from its original length, the blade retains its signature and displays remarkable condition for a sword approaching 700 years of age.

Physical Characteristics of the Blade

The Kōsetsu Samonji is a strikingly powerful sword that conveys both elegance and martial authority. The blade measures approximately 78.1 cm in length with a curvature of about 2.4 cm. It is crafted in the shinogi-zukuri style with a rounded back ridge (maru-mune), featuring a broad body width and a moderately extended tip — characteristics that suggest a grand, imposing presence.

The jigane (steel surface) displays a tightly forged ko-itame grain pattern with abundant ji-nie and chikei, creating a surface that seems to shimmer with inner light. The hamon (temper line) has been variously described as notare (undulating) mixed with gunome (irregular wave-like peaks), or alternatively as ō-midare (large irregular pattern) with pronounced ashi (legs extending from the hamon). The strong nie and brilliantly clear nioiguchi are characteristic of the Sōshū tradition that Samonji so masterfully adopted.

The bōshi (temper pattern at the tip) shows distinctive features on each side: the front displays a slightly pointed pattern with sweeping marks, while the reverse shows an irregular pattern that rises sharply and returns deeply. Both sides bear grooves (bō-hi) with rounded endings. The tang has been shortened, with five peg holes, and bears the inscription "Chikushū-jū Sa" in fine chisel strokes on the front near the ridge.

Accompanying the blade is an uchigata-na koshirae (sword mounting for wearing edge-upward) commissioned by Tokugawa Ieyasu. This mounting features polished sharkskin covered in black lacquer (kuro-urushi togidashi zame), representing a robust and dignified style befitting a great lord's personal weapon.

A Blade That Witnessed History: The Provenance of Kōsetsu Samonji

The name "Kōsetsu" derives from the sword's most famous early owner: Itabeoka Kōsetsu-sai (also known as Okabe Nagashige), a senior retainer and skilled diplomat of the Late Hōjō clan, the powerful samurai family that controlled the Kantō region during the Sengoku period. Kōsetsu-sai was renowned as a man of culture and learning, well-versed in tea ceremony and waka poetry, as well as a formidable negotiator.

When Toyotomi Hideyoshi launched his siege of Odawara Castle in 1590, the Hōjō clan fell. According to one tradition, Kōsetsu-sai was brought before Hideyoshi, where he reportedly displayed remarkable composure, stating that his clan had withstood a siege by the greatest army in the land for over a hundred days and that he had no regrets — he invited Hideyoshi to take his head. Moved by this display of loyalty and courage, Hideyoshi pardoned Kōsetsu-sai and eventually welcomed him into his own circle of close companions (otogi-shū). The sword was subsequently presented to Hideyoshi and later passed to Tokugawa Ieyasu.

Ieyasu, who treasured the blade, later bestowed it upon his tenth son, Tokugawa Yorinobu, the founding lord of the Kishū branch of the Tokugawa family. Yorinobu is said to have carried the Kōsetsu Samonji into battle during the Siege of Osaka. For generations thereafter, the sword was preserved as a prized heirloom of the Kishū Tokugawa family.

In the modern era, the sword passed through several private collections. In 2018, it was generously donated to the city of Fukuyama as part of the "Komatsu Collection" — a remarkable gift of 14 swords including 7 National Treasures and 6 Important Cultural Properties — ensuring that this magnificent blade would be preserved for public appreciation at the Fukuyama Museum of Art.

Highlights and What to Look For

When viewing the Kōsetsu Samonji, visitors should pay special attention to several remarkable features:

• The nie and nioiguchi: Look for the bright, crystalline particles (nie) along the hamon boundary. The brilliance and clarity of this line is one of the defining qualities that set Samonji's work apart and demonstrate his mastery of the Sōshū tradition.
• The jigane (steel surface): The tightly forged grain pattern with its shimmering ji-nie and dark chikei lines creates a mesmerizing depth that seems to change with every subtle shift of light.
• The signature: The inscription "Chikushū-jū Sa" (筑州住左) in delicate chisel work is considered exceptionally beautiful, often compared to brushwork calligraphy. This signature is one of the rarest in all of Japanese sword history.
• The sword mounting (koshirae): The black lacquer polished-sharkskin mounting commissioned by Tokugawa Ieyasu is a superb example of Momoyama-period sword furniture, reflecting the practical yet dignified taste of the great unifier.
• The overall sugata (form): Even after being shortened from its original length, the blade retains a powerful, imposing presence with its broad width, graceful curvature, and commanding tip — qualities that distinguish a true masterwork.

The Fukuyama Museum of Art: Home of Legendary Blades

The Fukuyama Museum of Art is situated within the verdant grounds of Fukuyama Castle Park, just a short walk from JR Fukuyama Station. The museum houses an impressive collection that spans European modern art, Japanese modern and contemporary paintings, and — thanks to the Komatsu Collection donation — one of the finest assemblages of historic Japanese swords in the country.

In addition to the Kōsetsu Samonji, the museum's sword collection includes another National Treasure by Samonji: the Taikō Samonji, a tantō that was once a personal favorite of Toyotomi Hideyoshi. Having two National Treasure blades by the same rare master swordsmith in a single museum is an extraordinary occurrence that makes the Fukuyama Museum of Art a must-visit destination for anyone interested in Japanese swords.

The museum hosts special exhibitions featuring its sword collection approximately once a year, and pieces from the collection are also occasionally lent to exhibitions at other institutions across Japan. Visitors are encouraged to check the museum's official website for the latest exhibition schedule before planning their trip.

Surrounding Attractions

A visit to the Fukuyama Museum of Art can easily be combined with exploration of the many cultural and scenic attractions in the Fukuyama area:

• Fukuyama Castle: Located adjacent to the museum, this castle was built in 1622 by Mizuno Katsunari. The reconstructed five-story keep houses a museum of local history, and its north face features Japan's only iron-plated castle walls, restored in 2022 for the castle's 400th anniversary. The Important Cultural Properties of the Fushimi Yagura turret and Suji-gane Gate, both relocated from Kyoto's Fushimi Castle, are especially noteworthy.
• Tomonoura: About 30 minutes by bus from Fukuyama Station, this picturesque port town has served as a tidal-waiting harbor since ancient times. Its Edo-period streetscapes, historic stone lantern, and connections to the tale of Sakamoto Ryōma make it one of the most atmospheric coastal towns in Japan.
• Myōō-in Temple: This ancient Shingon temple possesses two National Treasures: a Main Hall dating from 1321 and a Five-Story Pagoda from 1348, making it a rewarding destination for admirers of medieval Japanese architecture.
• Hiroshima Prefectural Museum of History (Kusado Sengen Museum): Located near the Fukuyama Museum of Art, this museum features a life-size reconstruction of the medieval town of Kusado Sengen, offering a vivid window into daily life in medieval Japan.