A Masamune Blade Renamed by Its Owners
This katana carries no swordsmith's signature on its tang, yet it ranks among the finest works of Masamune, the most celebrated swordsmith in Japanese history. The reason for the absent signature lies in the gold characters inlaid along the tang, which record the blade's later handling rather than the hand that forged it. They state, in part, that the sword was "possessed by Jo Izumi-no-kami," that it is a shortened Masamune, and that it was certified by a member of the Hon'ami family of sword appraisers.
The blade dates to the Kamakura period, the late thirteenth to early fourteenth century, and was made in Sagami Province, today's Kanagawa Prefecture. It now belongs to the Tokyo National Museum in Ueno. Collectors know it by two nicknames taken from its owners: "Jo Izumi Masamune," after the warrior who once carried it, and "Tsugaru Masamune," after the daimyo house that later kept it for generations.
Who Was Masamune
Masamune worked in the city of Kamakura during the closing decades of the Kamakura period, an age shadowed by the Mongol invasions and the approaching fall of the shogunate. He trained under Shintogo Kunimitsu, regarded as the founder of the Sagami school, and brought its methods to their height. Sword historians credit him with perfecting the Soshu-den, one of the five great regional traditions of Japanese swordmaking.
His name drew students from across the country. Later generations gathered his leading followers into a list called the Masamune Jittetsu, the "Ten Disciples of Masamune." That grouping comes from texts written long after his death, and several of the named smiths could not have studied with him directly. Having no son of his own, Masamune adopted the smith Sadamune as his heir. Few of his blades carry his signature, which is why so many Masamune works, this one included, were judged and labeled by appraisers in later centuries.
What the Gold Inscription Records
An old appraisal register called the Umetada Meikan dates the gold inlay to the sixth month of Keicho 14, the year 1609. By that account, the polisher and metalworker Umetada Jusai shortened the blade, and Hon'ami Kotoku, a leading sword connoisseur of the early Edo period, judged it to be Masamune's work and added the gold characters. The closing element of the inscription is a stylized monogram, a kao, which stands in for Kotoku's name.
The shortening explains the missing original signature. A swordsmith cut his name into the lower part of the tang. When a blade was trimmed from the base to suit a newer style of wear, that signed section was lost. Such reworked blades are called o-suriage, "greatly shortened." For a famous unsigned blade, a gold-inlaid attribution by a trusted appraiser worked as both a certificate and a mark of prestige.
Reasons for Its National Treasure Status
The sword became an Important Cultural Property in 1936 and was raised to National Treasure in 1951. The official commentary describes it as showing Masamune's character with rare clarity, calling it brighter and more open in its forging and tempering than the work of Norishige, a contemporary often named alongside him. Among surviving Masamune blades, this one is frequently singled out as the most representative of his style.
What sets it apart is the activity in the steel. The forging pattern is a wood-grain itame, threaded with dark lines called chikei. Bright crystalline particles known as nie lie thickly across the surface, and patches of drifting nie called yubashiri float above the temper line on one face. The temper line itself, the hamon, runs in gentle waves mixed with small irregularities, crossed here and there by glittering streaks of nie called kinsuji. These effects, prized far above mere sharpness, are the visual signature that built Masamune's reputation.
The Warriors Behind the Names
The owner named in gold, Jo Izumi-no-kami, was the warrior Jo Kagemochi. He served the warlord Takeda Shingen and later joined the forces of Tokugawa Ieyasu, rising to the rank of hatamoto with a stipend of seven thousand koku. His fortunes turned at the Winter Siege of Osaka in 1614, where he was stripped of his holdings for breaking military orders and withdrew into seclusion. One reference work suggests he parted with the blade around this time.
The sword then entered the keeping of the Tsugaru family, lords of the Hirosaki domain in what is now Aomori Prefecture, far to the north of Honshu. Records do not fix the exact year it arrived, but the family's own sword registers point to an early date, after which it stayed as a prized heirloom. Unlike many famous Masamune blades, it does not appear in the Kyoho Meibutsucho, the Edo-period catalog of celebrated swords, which makes its survival and documentation all the more valuable.
Seeing the Sword in Ueno
The blade is held by the Tokyo National Museum, Japan's oldest museum, founded in 1872 and set within Ueno Park. Japanese swords appear in the Honkan, the main Japanese gallery, where the metalwork room shows blades together with fittings and armor. The museum rotates its holdings, so any single National Treasure sword goes on view only during set periods rather than year round. Visitors hoping to catch this particular blade should check the museum's exhibition schedule before traveling.
Even when this sword rests in storage, the galleries usually hold other important blades, and the same building presents painting, sculpture, lacquer, and ceramics across Japanese history. The surrounding park gives further reason to linger, with several major museums, a famous zoo, and broad walking grounds that fill with cherry blossoms in spring.
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Q&A
- Why does the sword have no swordsmith's signature?
- It was greatly shortened in 1609, and the lower part of the tang, where Masamune would have cut his name, was removed in the process. In place of a signature it bears a gold-inlaid attribution added by the appraiser Hon'ami Kotoku.
- Why is it called both "Jo Izumi Masamune" and "Tsugaru Masamune"?
- Both names come from its owners. Jo Izumi-no-kami, the warrior Jo Kagemochi, is recorded in the gold inscription, and the Tsugaru family of the Hirosaki domain kept the blade for generations afterward.
- Can I see this sword on display at any time?
- No. The Tokyo National Museum rotates its swords, so this National Treasure goes on view only during scheduled periods. Check the museum's website for current exhibition listings before you visit.
- What makes a Masamune blade so highly regarded?
- Masamune perfected the Soshu tradition, known for vivid activity in the steel such as bright nie particles, dark chikei lines, and kinsuji streaks crossing the temper line. This blade is often called the most characteristic of his surviving works.
- How do I reach the Tokyo National Museum?
- The museum sits in Ueno Park, about a ten-minute walk from the Park Exit of JR Ueno Station. It opens from 9:30 to 17:00, closes on Mondays, and offers later evening hours on certain days.
Basic Information
| Name | Katana, gold-inlay inscription "Jo Izumi-no-kami shoji / Masamune suriage Hon'a (kao)" |
|---|---|
| Smith | Attributed to Masamune |
| Period | Kamakura period (late 13th to early 14th century) |
| Designation | National Treasure (craft, sword) |
| Important Cultural Property | 18 September 1936 |
| National Treasure | 9 June 1951 |
| Count | 1 blade |
| Dimensions | Blade length 70.8 cm; curvature 2.2 cm; base width 2.6 cm; tip width 1.5 cm; point length 3.0 cm |
| Owner | National Institutes for Cultural Heritage |
| Location | Tokyo National Museum, 13-9 Ueno Park, Taito-ku, Tokyo |
| Viewing | Shown on rotation; not on permanent display |
References
- Database of National Cultural Properties, Agency for Cultural Affairs
- https://kunishitei.bunka.go.jp/bsys/maindetails/201/308
- Tokyo National Museum
- https://www.tnm.jp/
- WANDER Kokuho: Katana, Jo Izumi-no-kami / Masamune (Tokyo National Museum)
- https://wanderkokuho.com/201-00308/
- Touken World: Tsugaru Masamune (Jo Izumi-no-kami Masamune)
- https://www.touken-world.jp/search-noted-sword/tengasansaku/56572/
Last verified: 2026.06.12