古三原伝

Ko-Mihara designates the swords produced in Mihara in Bingo Province (modern Mihara City, Hiroshima Prefecture) primarily during the Nanbokuchō and Muromachi periods. Geographically positioned between the great Bizen tradition to the east and the Yamashiro tradition to the west, Mihara smiths developed a distinctly Yamato-influenced aesthetic—masame-admixed jigane and suguha hamon—that sets their work apart from both neighboring traditions in immediately identifiable ways.

The school was founded by Masaie in the early Nanbokuchō period, apparently carrying Yamato transmission techniques to Bingo. Unlike the flamboyant chōji-midare that Bizen perfected across the Seto Inland Sea, Mihara work favors clean, restrained suguha hamon with fine uniform nie and jigane with noticeable masame influence—a practical, clear aesthetic suited to the regional warrior culture of western Honshū. Subsequent smiths—Masatada, Kanenori, Yoshikane—maintained the school through the Muromachi period under the protection of the Kobayakawa clan, who ruled Mihara as a castle town.

Mihara swords circulated primarily among warriors of Bingo, Aki, and Suō provinces (modern Hiroshima and Yamaguchi), satisfying a regionalized demand that the dominant Bizen industry did not entirely capture. The Mōri clan's consolidation of western Japan in the late Sengoku period created new demand from Mōri retainers, but the school's output remained modest compared to the great production centers.

Genuine Ko-Mihara blades are uncommon on the market, and confirmed signed examples are rare enough to command significant premiums among specialists. The school's relative obscurity compared to Bizen means that Mihara attributions—when correctly identified—sometimes represent undervalued quality for the knowledgeable collector. The quiet beauty of suguha on masame-influenced jigane represents a distinct aesthetic register that enriches understanding of the full range of Japanese sword beauty.