Ko-Naminohira is the collective designation for the early smiths and works of the Naminohira school of Satsuma Province whose activity does not extend later than the period. Tradition holds that in the late period, around the Eien era (987-989), a swordsmith named Masakuni came from Yamato and settled at Naminohira in Taniyama District, becoming the founder of the lineage. His son is said to have been Yukiyasu, and thereafter the school continued in unbroken succession down to the Bakumatsu shinshin-to era -- a span approaching nine hundred years. Within the period, the school adhered conservatively to inherited classical manners of workmanship, and for this reason precise dating among Ko-Naminohira pieces can often be difficult. Their style strongly reveals a Yamato temperament, yet the school developed a character distinctly its own, and features common to other old Kyushu works such as Yukihira and Miike Mitsuyo are also observed.
Surviving blades attributed to Ko-Naminohira characteristically display construction with high , marked taper from base to tip, deep , and -- an archaic form of elevated dignity. The forging is typically that flows overall and tends toward , sometimes taking on an -like appearance; the grain frequently stands (), and fine adheres well with present. A whitish cast pervades the steel, and appears distinctly. Compared with Yamato works made in their original province, the in both and tends to be finer, the conveys a viscous, soft quality described as sticky (), and the is subdued with a conspicuous tendency. The is chiefly a narrow , at times mixed with shallow or slight , accompanied by , , , and occasional . A distinctive hallmark is the dropping of the temper at the base (). The is typically with , often showing at the tip.
Ko-Naminohira blades constitute precious material for the study of early Kyushu swordsmithing, and the finest examples are appraised as works not descending later than the early or mid- period. Particularly valuable are those retaining an form with original , which convey an archaic elegance that leaves nothing to be desired in demonstrating the salient features of the Naminohira tradition. In both and , the school's grounding in Yamato is clearly expressed, while the distinctively gentle, adhesive character of the steel and the soft luminosity of the set Ko-Naminohira apart as a tradition of quiet refinement and considerable historical significance.