The Aoe school is a group of swordsmiths that prospered in Aoe-no-sho, Bichu no Kuni (current Kurashiki, Okayama). Currently, there remain Aoe swords that were created from the Kamakura to Northern and Southern Courts periods. Among them, those created in the early to mid-Kamakura period are called "Ko-Aoe (old Aoe)." Sadatsugu is a swordsmith representing the Ko-Aoe style and it is said that he was invited to a forging event where former Emperor Gotoba gathered swordsmiths from across the country once a month for sword making. This sword shows a gentle appearance with a thin body and a small tip and has strong koshizori (a type of a blade curve where the deepest part of the curve is near the tang), a characteristic of Ko-Aoe swords. The fine-grained (itame) ground metal has black spots called sumihada, which is also a characteristic of Ko-Aoe swords. The hamon (literally "blade pattern," which is a visual effect created on the blade by the hardening process) shows komidare and kochoji while there is konie in the blade with distinctive ashi and yo (both activities or "hataraki" within the hamon), displaying complex variations.