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

　The Aoe school was established in the late Heian period in Aoe, Bichu no Kuni, which developed a unique style of its own different from the forging style of the neighboring Bizen no Kuni. Among the swords of the Aoe school, those made up to the mid-Kamakura period are called Ko-Aoe (old Aoe). Although there is another famous swordsmith named Masatsune in the Ko-Bizen school of the neighboring Bizen no Kuni, Masatsune who made this sword was a swordsmith of the Ko-Aoe school. Moreover, it is said that in the Bichu forge, Masatsune belonged to the Senoo group, which was different from a group of swordsmiths with a name containing "tsugu," such as Moritsugu, Tametsugu and Sadatsugu. While this tachi (a sword made to be worn with the cutting edge down) has become shorter due to later grinding, it still retains a classical shape with koshizori (swords with the deepest part of the curve close to the tang) and funbari (a blade that tapers towards the tip). The jigane (ground metal) features a wood grain pattern with black spots called sumihada unique to the Aoe school and clear utsuri (a white misty formation that runs parallel to the hamon in the ground metal) emerging from the shinogi (the ridgeline). The hamon (blade pattern) features a complicated variation, including komidareba (a pattern of small irregular form) with little difference in height and lots of konie (small martensite crystals), ashi (martensite crystals) and yo (a falling leaf-like activity) in the hachu (the area between the nioiguchi (the crystalline structure which forms along the cutting edge of a blade as a result of the hardening process) and the cutting edge).