Early to Mid Muromachi

Establishment of the Muromachi Shogunate

Following the reunification of the Northern and Southern Courts in 1392 (Meitoku 3), the third shogun Ashikaga Yoshimitsu brought the Muromachi shogunate to its zenith. Yoshimitsu pioneered the brilliant Kitayama culture, represented by the Kinkaku-ji, and initiated Japan-Ming trade (kanagō trade) to deepen continental exchange. In the era of the eighth shogun Ashikaga Yoshimasa, Higashiyama culture flourished, with the Ginkaku-ji, shoin-zukuri architecture, tea ceremony, ikebana, and Noh theater—many of the foundational arts of Japanese culture—reaching maturity. Under this stable cultural environment, the realm of swords underwent profound transformation.

Changes in Sword Design

With the end of the intense warfare of the Nanbokuchō period, practical demand for ōdachi rapidly declined, and sword proportions converged toward more moderate dimensions. Blade length settled at approximately 2 shaku 3 sun to 4 sun (about 69–72 centimeters), with widths becoming somewhat narrower and ridges slightly thinner. Graceful forms with saki-zori (curvature toward the tip) became the standard. During this period, the transition from tachi (worn edge-downward) to uchigatana (worn edge-upward at the hip) gradually began, foreshadowing the uchigatana-dominated era established in the later Sengoku period.

Diversification of Styles

In the Bizen tradition, during the Ōei era (1394–1428) the brothers Osafune Morimitsu and Yasumitsu perfected a refined and elegant style termed "Ōei Bizen." The hallmark of Ōei Bizen lies in its beautiful, densely grained iron with fine itame structure, paired with sophisticated temper patterns of nioi-deki choji midare. In marked contrast to the grandiose vigor of the Nanbokuchō period, this style pursued elegance and refinement, displaying high artistry reminiscent of the masterpieces of Nagamitsu and Kagekiyo from the late Kamakura period. Morimitsu was particularly renowned for his tantō, many of which are known to bear fine carving. Yasumitsu, a master craftsman equal to Morimitsu, left celebrated works in both tachi and uchigatana; both artisans' pieces command high regard among koto blades today. Osafune Iesuke, an accomplished smith in Morimitsu's lineage, continued the Ōei Bizen tradition, and his signed works display dignified temper patterns faithfully inherited from his master's style.

In the Mino tradition, this was an era of rapid ascendancy for the Seki smithing community. Seki, blessed with superior soil and pine charcoal, possessed ideal geographical conditions for blade production. Smiths such as Kanetsune, Kanefusa, and Kanemitsu forged numerous practical and sharp swords, establishing the foundation that would later earn Seki blades their nationwide reputation in the Sengoku period. In the Yamashiro tradition, Shin'okunika (second-generation Shin'okunika) continued his predecessor's style while working in Kyoto. In the Yamato tradition, smiths of the Kanenaga line continued forging around Nara temples and shrines.

Notable Craftsmen and Events

A particularly significant development of this era was the large-scale export of Japanese swords undertaken as part of Japan-Ming trade. Under the kanagō trade initiated by Ashikaga Yoshimitsu, Japanese swords became a principal export commodity, with several thousand to tens of thousands of blades sent to Ming in a single trading mission. Osafune Bizen served as the primary production center for these export swords; the establishment of large-scale production systems further strengthened the organizational power of Bizen smithing. Export blades were sometimes fashioned in the "Tōyō" (continental) style to suit Ming tastes, yet the sharpness of Japanese swords was highly prized in the Ming court, celebrated even in poetry.

Historical Significance

The era before the Ōnin War (1467) represents, within the late koto period, a time of comparatively gentle and culturally mature workmanship, holding important significance as a transitional period between the grandiosity of the Nanbokuchō and the practicality of sue-kotō. Ōei Bizen pieces are relatively abundant with surviving signatures, placing them among the more accessible category of koto blades; for this reason, discerning collectors regard them as an entry point for koto collecting.