Harima Daijō Fujiwara Tadakuni was the second son of Sōemon Yoshiie (also written Hirosada), a disciple of the first-generation . He styled himself Hashimoto Rokurōzaemon, and his elder brother was Kunihiro. In 'ei 11 (1634) he received the court title Harima Daijō and changed his name from Hironori to Tadakuni, later advancing to the title Harima no Kami. He was retained by the Ogi Domain -- one of the three branch domains of the Saga Nabeshima house -- where he was active as an official domain smith. In his later years he took religious vows and adopted the art name Kyūtetsu, dying in Genroku 4 (1691) at the extraordinary age of ninety-four. While there were several generations who used the name Tadakuni, "in particular the first and second generations are regarded as especially skilled."
Tadakuni's body of work divides into two principal modes. His displays a broad, clear temper with and entering well; the is deep, with thickly adhering , and fine and appear -- producing what the consistently describe as a notably clear () effect in both and . Yet "his hallmark lies in with long in which stands out prominently." In this mode, the is typically mixed with , angular forms, and -like elements; the is taken wide; and enter "well and frequently"; and the is bright, with vigorous and running through the valleys of the . The forging is characteristically a dense , often mixed with , with very fine adhering thickly and fine entering in abundance. A remarkable subset of his achieves a full-blown -- with , , and -- that "is thought to have aimed in the direction of Hiromitsu." Such works are "extremely rare" within the period, "virtually without parallel within the main line aside from a single example each by the first and second generations of Tadahiro." Even in these ambitious departures, the -like forging and the way gathers in the valleys betray the unmistakable character of a blade.
The evaluations return repeatedly to the vigor and forcefulness of Tadakuni's workmanship. Individual blades are praised as "an especially successful work" (kaishin no ippō), as "one of his representative works" in which "he displays his full strengths," and as demonstrating "an impressively florid result." The deep , thickly adhering , the prominence of throughout the , and the brightness of the are identified as his defining signature across both and modes. His robust -- wide , slightly long proportions, and thick -- further contributes to a sense of commanding presence. Among the smiths working outside the main line, Tadakuni stands as the foremost figure of the Ogi branch, a master of exceptional range whose works in with long and vigorous constitute one of the most recognizable styles of the early era.