Ko-Bizen — Tomonari and Masatsune's Bizen Swords: The Oldest Stratum from Late Heian to Early Kamakura

The Oldest Layer of Bizen Swords

The ko-bizen-ha refers to a group of sword makers who were active in Bizen Province (present-day eastern Okayama Prefecture) from the late Heian period through the early Kamakura period. Later, Bizen would flourish with major schools such as the Ichimoji and Osafune lineages, but the earliest generation of sword makers that preceded them are collectively known as ko-bizen.

Bizen was blessed with high-quality iron sand and favorable water transport, making it a major center of sword production from ancient times. The ko-bizen-ha is positioned at the starting point of this long history.

The Historical Context of the Late Heian Period

The late Heian period when ko-bizen emerged was a major turning point in the history of the Japanese sword. It was the era when curved swords with sori replaced the straight chokuto of earlier times, establishing the form we today call the "Japanese sword." It is thought that the rise of samurai power in various regions and increased demand for curved tachi better suited to mounted combat provided the backdrop for this transformation.

The sword makers of the ko-bizen-ha were craftsmen who bore the responsibility of this era when "the form of the Japanese sword was moving toward its completion." Their works embody the spirit of the process in which the new form of the curved sword was being refined, and their significance lies not merely in their age but in the fact that they exemplify the very origins of the Japanese sword.

Master Craftsmen: Tomonari and Masatsune

Among the master craftsmen who represent ko-bizen, the names of Tomonari and Masatsune are frequently cited. Both are considered ancient sword makers who are said to have been active in the late Heian period, and their works are noted for their antique elegance in tachi form and a rustic yet powerful character that distinguishes them from Bizen swords of later eras.

Their works typically display high sori in the hips, showing elegant tachi forms, with jihada that is fine with tightly packed ko-itame, and hamon that tends toward the gentle—based on ko-midare or suguha patterns. Unlike the later Ichimoji school, known for its brilliant choji, the charm of ko-bizen lies in its antique refinement.

Style in Greater Detail

Ko-bizen tachi most commonly feature the kosori silhouette—strong curve at the hip that shallows toward the point—with small kissaki, giving an overall slender and elegant impression. The tapered profile, where the point is narrower than the handle, displaying a braced and stable appearance, is a characteristic feature common to tachi of the late Heian through early Kamakura periods.

The jihada shows tightly packed ko-itame with nie, presenting a lustrous, supple appearance. The hamon is known to feature ko-midare with admixed ko-choji, or suguha with fine details, all characterized by restrained and gentle hardening. Subtle effects such as kinsuji or sand-flow patterns may be visible within the blade, and while the work may appear subdued at first glance, the more one examines it, the greater depth it reveals.

The Rarity of Surviving Examples

Surviving works from the late Heian through early Kamakura periods are limited in number. Many long tachi were polished and shortened (suriage) in later periods, losing their signature blades; ko-bizen works that retain both their original form and signature are extremely valuable as historical records. Furthermore, the older a work is, the more unavoidable are effects of polishing wear and fatigue, making pieces in sound condition even rarer. This rarity is one reason why ko-bizen is spoken of with such particular reverence among sword enthusiasts.

The Legacy Flowing to Later Bizen Swords

The tradition of the ko-bizen-ha was inherited by the Ichimoji school, beginning with Fukuoka Ichimoji, and later by the Osafune school, as Bizen swords entered their golden age in the Kamakura period. Ko-bizen stands as an indispensable source for understanding the magnificent lineage of Bizen swords.

Viewing the genealogy of Bizen swords through the broad arc of "ko-bizen → Ichimoji → Osafune" makes the stylistic changes across each era easier to understand.

Points for Appreciation

When appreciating ko-bizen works, one should focus on the antique elegance of the tachi form and the gentle, refined hamon. The essence of appreciation lies in perceiving the serene beauty unique to this earliest generation, which differs from the more brilliant Bizen swords of later times.

When viewing an actual work, examining it in the following sequence will gradually reveal the rich detail concealed within its restrained style.

1. First, step back and observe the overall form, noting where the center of the curve lies and how the balance between the handle and point widths compares
2. Next, examine the jihada closely, observing the fineness and luster of the grain and the presence or absence of nie
3. Finally, trace the hamon, seeking out subtle midare and details within the blade

Additionally, it is helpful to compare photographs of late Heian tachi with those of Kamakura mid-period and later tachi in museum displays and publications. Once you can feel the difference in form, the antique refinement of ko-bizen will stand out all the more strikingly.

That said, works as old as ko-bizen rarely come on the market, but should you have the opportunity to consider a purchase, be sure to verify the presence of a reliable certificate of authenticity and carefully review its contents regarding the attribution. The older a work is, the more likely it is to be unsigned or have been shortened, making authentication documentation the foundation of value assessment. The condition of preservation—including the degree of polishing wear and presence or absence of defects—also carries significant weight in evaluating period pieces. Since photographs alone cannot fully convey the luster of the grain, it is important to clarify any concerns with the seller and form your judgment only after you are satisfied.

TOUKENZA presents Japanese swords in the Bizen tradition online, complete with photographs and commentary. Those interested in the history of ko-bizen and Bizen swords can browse and purchase works from our online collection. For any questions, please use our contact form.