Oku Motohira, common name Oku Kozaemon, was the eldest son and heir of Oku Motonao, born in Enkyo 1 (1744). He learned forging from his father and earned early a reputation for surpassing his teacher, his work appearing from the Meiwa era and rising sharply in volume from about An'ei 8 to 9. The published sources place him by a single recurring pairing that has held ever since: with Hoki no Kami Masayuki he is acclaimed as one of the soheki, the twin pillars of Satsuma , eleven years Masayuki's junior. His signature itself maps his career. In his An'ei and early Tenmei years he cut Satsuyoshi Motohira; from Tenmei 5 he cut Satsuhan- Oku Motohira; and after receiving the title Yamato no Kami in Kansei 1 (1789) he most often cut the long Oku Yamato no Kami Taira Ason Motohira. He worked into extreme old age, with a dated and age-inscribed piece from the very year of his death, Bunsei 9 (1826), at eighty-three.
His characteristic hand is a broad, imposing the sources name his favored -. The body is wide in with ample and an extended , and the temper is a shallow -toned into which he sets pointed , at times opened at the base, sometimes widening to . The is deep and the thick and strong with mixed, and through the run frequent and long , the streaming Satsuma -lines the published sources name imozuru, the yam-vine, recording on one that the enter thick to show "vine-like -lines" (「芋蔓状の沸筋」). The pointed teeth and the running vine are the spine of his recognition, a - read in coarse rather than in clove-flower.
The is the constant beneath. It is a well-forged , often a tightly packed with mixed , carrying thick and , on his finest pieces bright and clear. Over it the runs in or straight, turning back in , the point swept with and on his most vigorous work flaring to a flame-like cast. There is one feature the published sources single out as a point on the tang itself: the is almost always , narrowed toward the tip in a -like manner to a sword-shaped point, a form they note did not change throughout his life, the long signature cut boldly with a thick chisel and frequently carrying his age.
His record divides cleanly by period. The earlier work, dated through the An'ei years and into early Tenmei, is read as a calmer manner before the full hand emerges: a shallow -toned temper, at times a wide undulating into gentle , deep in with well-attached and a bright clear . The sources give it a name, reading one Tenmei 5 piece as a Shinkai-like shallow of his earlier phase and a Tenmei 2 piece, among his early works, as a Shinkai manner of the Osaka tradition. The forging beneath, the tight , is already the steel he carries into his prime, so the early is the hand held quieter rather than a separate school. He also forged often with his younger brothers Mototake and Motoyasu, who signed independently only rarely and whose skill the sources hold below his; joint signatures of two or three of the brothers survive and are themselves called precious, the workmanship on them no different from his sole-signed blades.
What sets him within his province is exactly the pairing the judges name and the manner they return to. He is read first against his elder townsman Masayuki, the two held together as the twin pillars of Satsuma , and the published sources keep returning to the description of him: his swords are generally, in their words, "broad in body and imposing" (「身幅が広く、堂々とした」), excelling in with much coarse in a flamboyant style, and he is the smith they say "excelled in the -" (「相州伝を得意」). His bright deep- with pointed , his running imozuru and his flaring are the grounded traits that set him apart, not a borrowed comparison. He stands at the head of the Oku line, the hand by which a Satsuma blade of his descent is read.
For the collector he is one of the great names of late Satsuma, and Fujishiro grades him Jo-jo . He has no National Treasures and no Important Cultural Properties; his record on the modern designation tiers runs through the rank, where twenty-six of his works are held, almost all and signed across a working life from An'ei to his death year, with one carrying the provenance of the Matsue Matsudaira family. Most designated blades, including those in private hands, are held rather than traded, and a fine signed Motohira of his characteristic - comes to market only from time to time and with patience, a substantial thing for a collector to encounter when it does. His work is, comparatively, among the more findable of the first-rank masters, more so than the locked heritage of the older traditions, but a dated, age-inscribed in his full vigorous manner remains a landmark acquisition, a document of how the Satsuma school reached its late summit.