Sadatsugu (貞次) is one of the most distinguished names in the lineage of Province. The earliest bearer, Sadatsugu, has been transmitted since the Kanchiin-bon Meizukushi as a master selected among the serving Retired Emperor Go-Toba. The Shinkan Hiden-sho assigns him the highest valuation: " workmanship, the finest, fifteen ," establishing the name as first-rank among works from the earliest period of critical appraisal. The group forged blades in the and Manju districts in the lower basin of the Takahashi River, and works through about the mid- period are distinguished as . The name Sadatsugu was inherited continuously from the early period through the close of the era. Among the later bearers, -ju Uemon Taro Sadatsugu, recorded as the son of Suketsugu, left dated works from the Karyaku, Gentoku, and Genko eras in the late period, though surviving examples are exceedingly rare. Osumi no Gon no Taira Sadatsugu, cited in the Kokon Kaji Biko with dated works spanning from Genko through Shohei, was one of the most active smiths of the period. A still later smith, identified as Saika Taro Hyoe no Jo Sadatsugu, left dated works from Joji through Shitoku. Separately, in Province, the first-generation Shimosaka Sadatsugu worked no later than the Keicho era as an influential close associate of the first-generation Yasutsugu, sharing the patronage of Honda Hida no Kami Narishige.
The Sadatsugu style establishes the technical vocabulary of the lineage. The is mixed with in which the grain stands out, presenting the characteristic texture; fine adheres densely, and fine enter. The is typically based on or , mixed with elements such as , , and small -like forms; and enter, the temper is -dominant with , and fine and run well, with the bright and clear. The signature is characteristically cut on the side with file marks. Osumi no Gon no Sadatsugu's workmanship reflects a particularly strong individuality within the school: he broadens the of the , forms thick , concentrates within the to produce -like scenery, lays intermittent along the edge to create a -like effect, and tempers the with deep . These features convey a bold, uninhibited flavor that overflows with vigor. The Shimosaka Sadatsugu of is distinguished by the prominence of in his work, forging a mixed with and descended from the Seki tradition, with a somewhat blackish tone to the steel and a tendency in the characteristic of the -Seki group.
The consistently characterizes the Sadatsugu works as possessing elevated dignity and ranks the name among the very finest of the tradition. Unsigned pieces of superior workmanship have from early times been appraised as "Sadatsugu" -- not necessarily indicating the individual smith, but signifying a representative and superior work of the school. Osumi no Gon no Sadatsugu is regarded as an "unusual presence" within the group for his vivid personal manner, and his finest works are evaluated as with both and described as . Throughout the lineage, the emphasize that surviving signed examples are extremely rare, lending each blade high documentary value for the study of the tradition. The continuous inheritance of the Sadatsugu name across nearly three centuries of production -- from a of the retired emperor through the final years of the period -- attests to the enduring authority of this lineage within the sword-making tradition.