National Treasures & Important Cultural Properties
of National Institutes for Cultural Heritage, Japan

Sadamune, commonly known as Hikoshirô, is thought to have been either the real or adopted child of the swordsmith Masamune. Sadamune was from Sagami Province (present-day Kanagawa Prefecture) and was active from the end of the Kamakura period (1185-1333) into the Nanbokuchô period (1333-1392). His style resembles Masamune's but is gentler and more regular. The tempering pattern on the blade is an irregular wave (J. midare) type. The sword was given the name "Tortoise-Shell Sadamune" (J. Kikkô Sadamune) because the engraving on the tang-a chrysanthemum within a hexagon-resembles a tortoise shell.

The branch of the Tokugawa family living in Owari Province (present-day Aichi Prefecture) presented the sword to Shogun Tsunayoshi (1646-1709) in Genroku 11 (1698).