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 "Sada" (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 NBTHK 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 tachi 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 masame-hada, with fine ji-nie adhering well and chikei appearing, while nie-utsuri stands up toward the mune side. The hamon is predominantly suguha, characteristically laden with hotsure along the habuchi, and frequently showing uchi-noke, kuichigai-ba, and nijuba; ko-nie adheres well, with sunagashi appearing. The boshi is vigorously hakikake and finished in yakizume --- a hallmark that the Koji-kiron describes as the manner of the Hosho Goro tradition: "They forge masame so that it stands out conspicuously, and the boshi is bluntly finished in yakizume, without any concealment." In many works, the yakiba becomes broader and the nie intensifies from the monouchi upward. The nakago typically shows higaki yasurime, and Sadaoki's signatures range from the two-character "Sadaoki" to the full "Yamato no Kuni Fujiwara Sadaoki."

Sadaoki's surviving corpus encompasses both tachi and tanto, the latter in hira-zukuri form with characteristic thick kasane and slight uchizori --- features the NBTHK identifies as hallmarks of Yamato construction. Across the designated works, the NBTHK consistently affirms that his jigane and hamon "leave nothing wanting in showing the archetypal workmanship of this school" and "perfectly express the quintessential style." Several pieces are described as kenzen --- 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.