Yasutsuna is the foremost representative swordsmith of the Ko-Hōki tradition, active in Hōki Province during the late period. Although traditional sword reference works such as the record his working dates as the Daidō era (806–810), modern scholarship, based on careful analysis of his extant oeuvre, places him considerably later — roughly contemporary with Munechika and thus firmly within the latter decades of the period. Among the various smiths of ancient Hōki, Yasutsuna is distinguished by the comparatively large number of signed works that survive, and his renown has been further elevated by the existence of the celebrated Dōjigiri Yasutsuna, widely regarded as one of the supreme masterworks of the Japanese sword.
Yasutsuna's characteristically exhibit an elegant form with pronounced , evident , and a conclusion in or , presenting a silhouette of refined archaic dignity. A distinguishing feature of his geometry, as compared with works, is that the tendency toward a drooping tip () is not especially conspicuous. In forging, the displays mixed with and , with the grain standing out prominently (); thick adheres abundantly, interwoven with , and the steel assumes a characteristically blackish kana-iro tone. — a mottled shadow pattern — appears distinctly along the surface. The is typically built on a foundation of or with shallow , into which , , and intermingle. The temper is thickly suffused with , and along the one observes abundant , , and in places and , producing a rich profusion of vertical activity at the boundary between hardened and unhardened steel. In many examples the temper shows at the base near the , a trait that further distinguishes the Ko-Hōki manner from that of contemporaneous lineages. The most commonly runs straight, finishing in or , at times with vigorous . Yasutsuna's two-character signature follows a consistent habitual arrangement in which the character 綱 () is cut larger than 安 () and is set slightly to the right, a reliable diagnostic feature in authentication.
Yasutsuna occupies a foundational position in the history of the Japanese sword as a master who represents the earliest fully developed phase of production outside the heartland. His work demonstrates a technical idiom — marked by bold forging textures, deep activity, and a restrained yet complex temper line — that is distinct from the group and constitutes the defining aesthetic of the Ko-Hōki school. The finest examples among his surviving display preservation in both and , with workmanship of the highest order, and they remain essential reference points for understanding the diversity of swordsmithing traditions in the formative era.