Yukihira of Bungo Province (豊後国行平) ranks among the Kyushu koten- (classical group) as the smith of the highest technical accomplishment and reputation, and a comparatively large number of his works survive today. Known by the title Kishin Dayu, he is variously transmitted as either a disciple of, or conversely a teacher to, the Hikosan monk Sadahide, while other traditions name him Sadahide's son. He is also counted among the — appointed smiths serving Retired Emperor Go-Toba. Among his extant works there is a bearing a dated inscription of Genkyu 2 (1205), by which his period of activity in the early is established with considerable clarity. Yet at first glance, as the repeatedly observes, his workmanship "presents a style that appears even older," and his manner is described as notably archaic even within the classical early Kyushu tradition. His style is "entirely close" to that of Sadahide, and resonates with other old Kyushu works such as Ko-Naminohira and Ko-Hoki.
Yukihira's forging is consistently described as soft, — viscous and tenacious — possessing a distinctive color and luster. The shows mixed with or , with fine adhering thickly and delicate entering, often producing (whitish ). His is either or , and in every case the tends toward — a moist, soft quality that is perhaps his single most defining characteristic. The habitual manner of , dropping the temper above the , is likewise shared with Sadahide and constitutes a signature trait. His typically present a slender with , high , and pronounced , expressing what the term an "elegant " continuous with the refined forms of the period. Yukihira's blades frequently bear carvings of , and one also encounters Jizo Bosatsu, , matsukui-zuru (cranes feeding on pine), and cherry blossoms — carving types "not found in works prior to him." Contrary to the general practice of swordsmiths of his time, he customarily cut his signature on the side, a distinctive convention noted in virtually every .
Across two decades of evaluations, from the earliest sessions through the most recent designations, Yukihira's works are praised in strikingly consistent language: the softness perceptible in the forging, the -tending , and the "clearly express the smith's manner" and "evoke the distinctive flavor of the Kyushu classical tradition." Pieces are repeatedly judged as "typical examples" in which "the characteristic features of this smith are clearly and markedly expressed," yielding what the examiners call an "archaic and dignified excellence." Within the classical sphere of Kyushu work, these qualities "especially convey an archaic and dignified excellence," while individual pieces are further noted for their "elegant refinement" and a (archaic elegance) that permeates both and . Within the Kyushu koten-, Yukihira occupies a position that the affirms without qualification as preeminent — a smith whose work, whether encountered as full-length , , or the relatively rare , fully displays the working range and particular charm of the oldest Kyushu forging tradition.