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

The Aoe school was a group of swordsmiths that prospered in Aoe-sho, Bicchu no Kuni (current Kurashiki, Okayama) and the swords created from the Kamakura to Northern and Southern Courts periods remain now. Among these remaining swords, those forged from the early to mid-Kamakura period are called "Ko-Aoe (old Aoe)" and Yasutsugu is known as a representative swordsmith of Ko-Aoe. This is a sword with koshizori (a type of a blade curve where the deepest part of the curve is near the tang) forged in the early Kamakura period and demonstrates the fine-grained (mokume) ground metal called chirimenhada (literally "crape skin"), the ground metal unique to the Aoe School. The hamon (wave pattern on the surface) is komidare (small wave) with konie (small martensite/troostite crystals) and koashi (small extensions of martensite/troostite crystals extending from the hamon to the cutting edge). Since most Ko-Aoe swords do not bear the name of the swordsmith, this one with the inscription is a valuable piece and represents one of Norifusa's best.