The Gassan tradition is said to have originated in the mountain religion associated with the Dewa Sanzan (Three Mountains of Dewa Province), of which Gassan was one, sometime during the Heian period. However there are no known dateable swords with the characteristic sinosoidal undulating ayasugi hada [cryptomeria twill] of the school until the Nanbokucho and Muromachi periods, and the school had ceased to exist by the end of the Muromachi period.
A descendant of the Gassan smiths in Dewa Province named Sadayoshi moved to Osaka in the middle 19th century and revived the old tradition there. Sadakazu, born in 1836, was adopted into the Gassan family in Omi Province as the son of Sadayoshi. After the Haito Kinshi Rei (law prohibiting the wearing of swords in public) of 1876 he continued with the family tradition despite there being little demand for swords. In 1906 he made a sword for the Emperor Meiji, and was appointed as a Teishitsu Gigei-In [Imperial Craftsman]. In 1916 Sadakazu made a further sword for the Taisho Emperor. He died in 1918 age 83. In addition to the ancient Gassan style with Ayasugi hada he made swords in the Soshu style, and like this blade in the Bizen styles. He was a competent sculptor and often made intricate carvings of Fudo Myo-o and his attributes in the form of the kurikara as on this blade. The Gassan tradition continues with the current master Sadatoshi and his son.