The Ko- -- the "old " -- designates the earliest phase of the Fukuoka school of Province, encompassing the generation of smiths active from the late through the early period before the school's celebrated mid- flowering into flamboyant . The founder of the lineage is Norimune, who stands at the precise transitional moment between the older tradition and the emerging idiom. Around him gathered a constellation of closely related smiths -- Muneyoshi, Narimune (transmitted as Norimune's second son), Sukemune, Munetada, Shigehisa, Sadazane, Yukikuni, and Sukenori -- several of whom were appointed as , swordsmiths in the personal service of Retired Emperor Go-Toba during the Shoji era. The consistently observes that the workmanship of these smiths differs markedly from the splendid, ornate style of the mid- masters: in and in the workmanship of and , they strongly preserve the flavor of , presenting what the designation records describe as "an older and more antique range of expression."
The Ko- collective style is defined by a classical of slender build with pronounced , evident , and compact -- an "unmistakably graceful silhouette" in the language of the designating body. The characteristically displays tightly knit or mixed with , bearing minute and fine , with conspicuous standing out in the . The is built on a -based foundation into which , , and are mixed, with abundant and , adhering well, and frequent and . This constitutes the school's prevailing mode -- restrained, archaic, and technically accomplished. Yet the group also encompasses a second, somewhat more assertive tendency visible in certain works by Muneyoshi and Munetada, where larger-clustered heads become conspicuous and occasional introduce greater fluctuation in the height. The consistently finishes in or with return. When compared with , the Ko- manner tends toward somewhat more conspicuous and orderly with clearer , yet it remains fundamentally distinct from the brilliant flamboyance of the mature Fukuoka expression. An additional point of diagnostic interest is that behavior varies within the group: while most members display vivid , Sadazane's works are notable for subdued or absent , a distinguishing feature the has specifically identified.
The Ko- tradition occupies a foundational position within the canon as the school from which the entire lineage would develop. Norimune's restrained yet technically accomplished manner established the base upon which the school's later, more exuberant style would be built. Muneyoshi, whose finest works are ranked among the foremost achievements of the tradition, presents the additional scholarly complexity of multiple hands behind a single name -- a plurality the has consistently documented. Narimune's blades, calm in feeling yet vividly revealing the appearance of Ko-, include examples bearing distinguished provenance from the Tokugawa shogunal house and the Imperial Collection. Sadazane, praised for that is "truly of excellent quality," inherited the style of while adding further novelty. Across the group, signed works are uniformly described as rare, lending pronounced documentary significance to each surviving example. The collective achievement of the Ko- smiths lies in having forged a coherent transitional idiom -- neither the austere archaism of nor the dazzling ornament of mid- , but a distinct aesthetic of restrained classical grace that the regards as among the most prized expressions of early swordsmithing.