A by Yoshisada dated Shōhei 13 (1358), cut on the reverse "ninth month, day" and on the face with the orderer's name "Shu Nagamasa," is the documentary anchor of his career: from it the published sources accept that he was a direct disciple of Ō-, and fix his working years in the middle of the fourteenth century. Yoshisada is a smith of the , or , school of , one of the -ichirui who carried the school's manner forward in the period beside Yasuyoshi, Yukihiro, Yoshihiro, Kunihiro and Hiroyasu. He is traditionally held to be "a son of Ō-", or at least a member of his immediate circle, and he signs simply "Yoshisada" or "Yoshisada ," a piece additionally cut "Chikushū jū" not being encountered.
His hand is read first through what the published sources allow him as his one personal characteristic. They observe that the smiths of the group show comparatively few individual tells, and then single Yoshisada out: "even within the group his becomes a small-patterned design, and in this lies his stylistic individuality". That small-scale is the through-line of his work. Among signed pieces two manners are drawn. One is a calm, shallowly undulating on a base; the other is a temper that resembles his schoolmate Yasuyoshi but is worked, in the judges' words, "a little smaller and more compactly than his". In both the adheres well, with fine and running through, the activity carried in and rather than in tall clusters, and the rising with a thrusting tendency to a pointed return.
The is the -derived steel the whole line shares, and it is the constant beneath both his manners. Over a standing mixed with and a flowing , the grain a little open, he lays thick and well-entered , the steel at times taking a darkish cast; on several blades a whitish -style drifts in the . Against that the temper stays comparatively small in scale. Where his quieter pieces run a gentle , deep in and bright, his more active pieces gather the into the compact pattern the sources name, with occasional coarser and, near the , and -like lending a varied scenery.
The two faces of his record sit side by side. The signed work is chiefly and : the transmitted in the Mito Tokugawa house, and wide, with strong in both and and a bright, clear , which the published sources call "an especially outstanding piece by this smith"; the dated Shōhei 13 bearing the orderer's name; and the Mononobe Yoshisada , which tempers the high into a brighter, livelier and shows how far the hand could open. The other face is the appraised as his, wide and powerful, several with an extended or large , a with some feeling over the standing , a carved through; the judges note that even these unsigned attributions tend to the small-patterned , so the body of his oeuvre is read through that small rather than through any single signed tell. One such carries a gold-inlay attribution to Yoshisada by Mitsunori.
What sets Yoshisada apart within the group is precisely that small-patterned temper. Where Yasuyoshi's stands fuller, Yoshisada's is drawn smaller and more compact; where the line as a whole is read as showing few individual features, his compact , bright and pointed, thrusting recur from blade to blade as his own. He belongs to the generation that held the school together after Ō-, neither the founder's brilliance nor a late epigone, but a sound and recognizable hand whose individuality the locates in scale rather than in flamboyance.
For the collector he is a documented but uncommon name. Fujishiro grades him Jō-jō . He has no National Treasures and no Important Cultural Properties; his record runs instead through four and forty-three blades, with two holding the prewar Jūyō Bijutsuhin, one of them the Mitsunori gold-inlay piece now in the Seikadō Bunko. His blades carry distinguished provenance: the Mito Tokugawa house, with pieces traced to Tokugawa Ieyasu and Yorifusa, the Mōri family, the Ikeda family, and the Shimazu and Satake houses, with examples on deposit at the Kyoto National Museum and held in the Seikadō Bunko. The signed work is genuinely scarce, and "surviving examples in form are exceedingly rare"; most of what survives is held rather than traded, but a -tier attribution or, less often, a signed or comes to light from time to time, and a privately held Yoshisada is a rewarding thing for a collector to encounter, a clear document of how the school read in the hands that carried it after its master.