Sadaoki was a swordsmith of the Hosho school, one of the five traditions of Yamato Province, traditionally said to have resided in Takaichi District. No dated works by Sadaoki survive; however, sword reference works place him around the Gentoku era (1329--1331), describing him as a son of Sadamune and a member of the lineage of Sadayoshi --- though an alternative tradition names Sadakiyo as his father. He belongs to a lineage in which the shared character "" (貞) unites the names of its principal smiths: Sadayoshi, Sadamune, Sadakiyo, Sadamitsu, and Sadaoki alike. The Fujiwara surname appearing in his signatures is a clan-name used within this line, seen also with Sadayoshi and Sadakiyo. The has observed that the dating to the Joji era given in some reference books "feels somewhat overly late," though without dated works the question remains open. Signed works by Sadaoki are exceedingly few, and signed are noted as extremely rare, making each surviving example precious documentary material.
Among the five Yamato schools, the Hosho is recognized as possessing the most markedly distinctive workmanship. Sadaoki's blades are forged in the school's archetypal tight , with fine adhering well and appearing, while stands up toward the side. The is predominantly , characteristically laden with along the , and frequently showing uchi-noke, , and ; adheres well, with appearing. The is vigorously and finished in --- a hallmark that the Koji-kiron describes as the manner of the Hosho Goro tradition: "They forge so that it stands out conspicuously, and the is bluntly finished in , without any concealment." In many works, the becomes broader and the intensifies from the upward. The typically shows , and Sadaoki's signatures range from the two-character "Sadaoki" to the full "Yamato no Fujiwara Sadaoki."
Sadaoki's surviving corpus encompasses both and , the latter in form with characteristic thick and slight --- features the identifies as hallmarks of Yamato construction. Across the designated works, the consistently affirms that his and "leave nothing wanting in showing the archetypal workmanship of this school" and "perfectly express the quintessential style." Several pieces are described as --- sound and well-preserved --- and praised for their refined, elegant silhouettes. Given the rarity of signed Hosho works, Sadaoki's extant blades are valued not only for their intrinsic quality but as indispensable reference material for the study of this most distinctive among the Yamato traditions.