Ohara Sanemori (大原真守) of Hoki Province is traditionally transmitted as a son of Yasutsuna, the founding figure of the Ko-Hoki school. Together with related smiths--Aritsuna, Sadatsuna, Yasuie, and Sanekage--this group flourished from the late Heian period into the early Kamakura period. Sanemori's signed works employ a comparatively long inscription, characteristically a six-character mei cut with a thick chisel, of which the variant closely resembling the tachi preserved at Wakayama Toshogu (Important Cultural Property) is the most frequently cited. Extant signed works are "exceedingly rare," and the several signature variants make definitive authentication a continuing subject of study.

The NBTHK consistently distinguishes Ko-Hoki from contemporaneous Ko-Bizen, noting that while both schools temper predominantly small-pattern midare, "upon closer examination their character differs somewhat." Sanemori's kitae is itame-hada mixed with mokume, with the grain tending to stand; fine ji-nie adheres, chikei enters, and jifu-like textures are intermingled with jifu-utsuri standing out. A defining feature is that "the steel often takes on a blackish tone." His hamon is based on suguha mixed with ko-midare, ko-choji, and ko-gunome--"overall a fine-patterned irregularity"--with ko-ashi and yo entering well. The nioiguchi tends toward urumi (a moist, soft quality) and at times shows shizumi (subdued character), while kinsuji, nie-suji, and sunagashi appear with frequency. The boshi is typically sugu to ko-maru, and carved works--placed characteristically at the koshi-moto--include bonji, suken, and koshi-bi, providing "valuable material for understanding the distinctive nature of Sanemori's carvings." Within the Ko-Hoki group, Sanemori's tempering is noted for presenting "somewhat smaller-scale patterns of irregularity" compared to Yasutsuna.

The setsumei repeatedly invoke an atmosphere of "archaic, artless dignity" and "rustic, provincial flavor" when describing these works, a quality that "in one vein recalls Awataguchi Kuniyasu and Ayanokoji Sadatoshi." The classical sugata--slender, with funbari, high koshizori, and ko-kissaki--is described as appearing "more frequently in this smith's work" than in his father's. Multiple blades bear the addendum character "Katsu" (勝) on the ura of the nakago, a feature of unknown meaning that is "valuable as documentary material," also recorded in the Tsuchiya Oshigata.