Sword with Gold Inlay, attributed to Masamune, owned by Jōizumi no Kami

Basic Information

Catalog ID: 201
Item ID: 308
Category: Crafts
Country: Japan
Period: Kamakura Period (1185–1333)
Date designated: June 9, 1951
Prefecture: Tokyo
Location: Tokyo National Museum (Ueno Park, Taito Ward, Tokyo)
Owner: Agency for Cultural Affairs / Tokyo National Museum

Source: Excerpted from the National Designated Cultural Properties Database (https://kunishitei.bunka.go.jp/bsys/index)

Overview

This tachi (single-edged long sword) is a masterpiece crafted by Masamune of Ashizu, one of the most renowned swordsmiths in Japanese history. It is known by the title Jōizumi Masamune and boasts an impeccable lineage: it was once owned by the Sengoku warlord Jōizumi no Kami Kagemichi, passed through Tokugawa Ieyasu, and ultimately remained within the Shogun’s family. The blade features a gold inlay inscription confirming its authenticity as a work of art from the Hon’ami family, giving it immense artistic and historical value.

Historical Background

In the late Kamakura Period, a new swordsmithing style known as Sōshuden (Ashizu school style) was established in Sagami Province (modern Kanagawa Prefecture). Masamune, credited with perfecting this style, sought to create increasingly durable and practical blades following the national crisis of the Genkok (Mongol Invasions). Originally a very long ōtachi, the sword was later shortened (Ōmashita) to its current form, adapting to changing battlefield tactics.

During the Azuchi-Momoyama Period (1573–1600), it was authenticated as an authentic Masamune piece by Hon’ami Kōtoku, a recognized authority on swordsmithing. The sword is named after Jōizumi no Kami Kagemichi, who served the Takeda and Hōjō clans before becoming a retainer of Tokugawa Ieyasu. It was later presented to Tokugawa Ieyasu and once bestowed upon Minono Katsunari, a meritorious official, but it was subsequently gifted again to the second Shogun, Tokugawa Hidetada. Since then, it has been carefully preserved as a family heirloom within the Edo shogunate.

Features and Appeal

This tachi is a concentration of Masamune’s exceptional skill and the aesthetic principles of the Ashizu school style.

Gold Inlay Inscription (Kin-zōganmei): Originally unmarked, Hon’ami Kōtoku recognized it as an authentic work by Masamune. The blade core bears “Masamune,” the owner’s name “Jōizumi no Kami,” and the seal of the Hon’ami family, all executed in gold inlay.
Beauty of the Nie: Strong formations of nie (iron crystals), visible to the naked eye, appear prominently on both the temper line (hamon) and the blade core, giving it a powerful yet ethereal glow.
Blade Core and Temper Line: The deep, rich patina of the blade core is beautifully balanced by the gentle, wave-like notare (curving) pattern of the temper line, creating an elegant and profound visual landscape.
Balance of Functionality and Artistry: It achieves supreme functional beauty—being “unbreakable, unbending, and sharp”—while simultaneously possessing overwhelming artistic dignity as a piece of craftsmanship.