Sekishu Sadatsuna is traditionally transmitted as a son of the first-generation Naotsuna, and his residence, like that of Naotsuna, was Dewa in Iwami Province. According to the sword reference works, there were as many as four generations bearing the name: the first is placed in the Shohei era, the second around the Meitoku era, the third in Oei, and the fourth in Kosho. As the period descends, later followers such as Shosue, Shosada, and Rinsho appear in the Nagahama area of the province.
Sadatsuna's workmanship resembles that of Naotsuna and displays clear affinities with the tradition (-). Examples are seen both in a style centered on and in a style centered on ; in either case, abundant and vigorously developed are the defining characteristics. The forging is typically mixed with , somewhat standing in grain (), with very fine thickly applied and entering well. A distinctive feature is the somewhat blackish cast of the steel (kanashoku). Within the , round-headed , angular elements, and intermix freely, and in places the run together in linked irregularity. and appear vigorously, with interspersed, and the shows strongly and . These features combine to produce works charged with vigor and expressive power.
Though signed works surviving from the period itself remain unknown, the designated examples attributed to Sadatsuna clearly manifest his characteristic traits: the blackish-toned forging, the linked irregularity of the , and the conspicuous activity of , , and coarser within the temper. Both and are charged with energy, and the finest examples among his works stand as forceful, well-made pieces that demonstrate the vitality of the Iwami swordmaking tradition during the period.