The school represents the earliest identifiable stratum of swordsmithing in Province, encompassing smiths active from the late period through the early period. Its twin pillars, Tomonari and Masatsune, are traditionally placed as early as the Eien era (987-989) and the late tenth century respectively, and together they established the aesthetic and technical foundation upon which the entire tradition was built. The school produced an extraordinary concentration of talent: Kanehira, celebrated since antiquity as one of the " Sanpei" alongside Takahira and Sukehira; Nobufusa, whose "Jumansoku" has been famous since the period; Kageyasu, whose distinctive style the positions "at a pivotal juncture in the development of swordmaking"; Yoshikane, one of the most prolific and consistently accomplished names in the school; and Yukihide, Naritaka, Sukekane, Toshitsune, and Tochika, each contributing signed works of the highest documentary value. Many names were borne by multiple generations, and the has observed across numerous designations that differences in signature scale, calligraphic style, and workmanship indicate several smiths sharing the name at slightly different periods.
The technical vocabulary, as it emerges across the collective testimony of the designation records, is defined by restraint, luminosity, and an archaic dignity the terms koko -- "archaic fragrance." The characteristic presents a slender build with high , pronounced , and , producing what the consistently describe as a graceful and dignified silhouette. The is forged in mixed with , frequently tending toward , with abundant and fine threading through the steel. -- whether , , or the partial -like formations the has called "an unfinished stage conveying an archaic, unsophisticated charm" -- stands across the ground, appearing with particular clarity in Masatsune's work, where it "rises with striking clarity" compared to the subtler manifestations in Tomonari's. The is fundamentally -based, mixed with , , and ; and enter well, adheres thickly, and and run throughout, producing a consistently described as "bright and clear." Along the hardened edge, intermittent and produce -like effects -- a trait especially associated with Yukihide and Sukekane but observed across the school. The is typically with turnback, often exhibiting . A tendency in the appears in certain smiths, notably Yoshikane, lending a subdued depth distinct from the brighter expressions found in Masatsune's corpus.
In the traditional comparative appraisal of the school's supreme masters, Tomonari is "especially notable for the excellence of " while Masatsune "surpasses him in the intricacy and excellence of the " -- a formulation repeated with near-canonical consistency. Kanehira's renown is elevated by the supreme named blade O-Kanehira, a National Treasure "counted among the foremost celebrated blades under heaven," while Nobufusa's works occupy a pivotal position at the transition from the late Fujiwara aesthetic to the emerging idiom. Toshitsune, as a worthy successor to Masatsune, demonstrates that even within the school's restrained vocabulary, imposing construction and florid were achievable without departing from the manner. Tochika bridges the heritage and the vigorous decorative impulse of the school, while Kageyasu's style "was later carried forward into Ko-," establishing a direct line of descent into the next great chapter of production. Works by smiths have been transmitted through the most distinguished collections in Japan -- the Imperial Household, the Tokugawa shogunal house, the Satake, Shimazu, Date, and Nabeshima families -- and the consistently affirms that both and remain with remarkable frequency, testifying to the supreme quality of the original steel. The school stands as the fountainhead of the tradition: its archaic dignity, luminous clarity, and refined -laden elegance define the standard against which all subsequent production is measured.