The Ko-Hōki school, encompassing figures traditionally beginning with Yasutsuna and including smiths such as Sanemori, Aritsuna, Sadatsuna, Sanekage, and Yasuie, flourished in Hōki Province from the late Heian period into the early Kamakura period. Hōki Province had long been known as a source of high-quality iron, and swordsmiths emerged there from an early date, producing some of the earliest extant Japanese swords. Works attributed to this group often appear unsigned, reflecting both the antiquity of the tradition and the practice of leaving blades mumei. While individual attributions remain uncertain for many surviving pieces, the collective body demonstrates a coherent regional workshop tradition distinct from other provincial centers.

The smiths of Ko-Hōki forged blades that at first glance resemble contemporaneous Ko-Bizen works, particularly in their use of ko-midare-based hamon patterns. However, closer examination reveals distinctive characteristics that set the tradition apart. The kitae typically shows large-pattern itame mixed with ō-itame and mokume, with pronounced hada-dachi (standing grain) and frequent incorporation of chikei and jifu (mottled surface textures), producing an overall dark, blackish cast to the steel. In the hardened edge, the nioiguchi exhibits an urumi (moist or soft) tendency, the habuchi becomes textured and stands out, and thick nie adheres strongly. The hamon frequently displays conspicuous kinsuji and sunagashi throughout, with small gunome and ko-notare elements emerging as mixed features. Construction details such as narrow shinogi-ji in proportion to blade width, abundant hiraniku, and the occasional presence of yakiootoshi at the machi further characterize the group's work.

This combination of technical features produces swords that, while sharing formal similarities with Ko-Bizen, convey a more markedly rustic, provincial character—what NBTHK appraisals consistently describe as an archaic and subdued flavor rich in yashu (untamed) qualities. The Ko-Hōki attribution encompasses works displaying these characteristics in varied combinations: some show primarily suguha-based temper with mixed irregularities, others present more complex small midare with chōji elements, and still others feature running gunome with pointed tendencies. Despite this variation in pattern, the fundamental qualities of standing, darkened forging with vigorous nie-based activities remain constant. The tradition's classical tachi forms—often with pronounced koshizori, evident funbari, marked taper from base to tip, and small kissaki—further enhance the archaic impression, creating works that reveal the essential character of early Japanese sword making while maintaining their own distinct regional identity within the broader landscape of kotō production.