In the second month of Genkyu 2 (1205), Yukihira of Bungo signed and dated a that still survives; retempered long ago, it is called precious by the published record as the document that fixes his activity at the turn of the and periods. He bore the appellation Ki no Shindayu (紀新太夫), worked in Bungo province in Kyushu, and stands at the head of the group the calls the Kyushu classical school: his designation texts open with the standing sentence that "within the Kyushu classical school his technique and fame are the highest, and comparatively many of his works survive" (九州古典派の中でも技術と名声が最も高く、現存する作品も比較的多い). Tradition binds him to the monk-smith Joshu, also read Sadahide, of Mount Hiko in the province, as the monk's pupil by most accounts, his teacher by others, his son by others still. He is also transmitted as one of the of the retired emperor Go-Toba. Even so, the sources note that at first glance his work appears older still.
His manner is described as wholly close to Joshu's. The forging is soft and viscous, the steel of the published sources, with a peculiar sheen (一種の色沢があり); the temper is or a small , and in either case the clouds softly in ; and the habit of dropping the temper above the in a is, the texts add, the hand in both men (区上で焼き落す手癖も同様). The is often large, running about half a above the , and it is fragile evidence: of one greatly shortened the sources note plainly that the has been lost to the shortening itself. His are slender with a small , the high and the marked, the curve falling away toward the tip; smallish blades of around two two are often met, and a truly large is called exceptional.
The is , in places flowing and occasionally showing larger grain, with fine, thick , delicate and a whitish that stands out against the soft steel. Over it the runs as a narrow mixing , and a shallow , with entering and adhering; faint and slight appear, and small drift along the , in places with a tendency. The is tempered low and runs into a small , at times in the manner of or with . One text gathers the whole into a sentence, "this is a quintessential by Yukihira of Bungo" (豊後の行平の典型的な太刀である): slender and small of , the a packed of viscous character, the a narrow with a little and a large , distinctive carvings at the base, the signature on the in artless characters.
Two registers carry his name beyond the steel. The first is the chisel. Most of his blades bear small, antique carvings at the , foremost a in relief within a , with , and at times a Jizo Bosatsu, a pine-eating crane, cherry blossoms or a within the groove; the published sources state that "carving of this kind is not seen in works before his" (この種の彫刻は彼以前の作には見当らない), and the imperial-collection texts add that the method was handed on to later Bungo work. A blade wholly without carvings is the rarity; of one such , once held by Tokugawa Iesato, Honma Junji wrote that its workmanship nevertheless ranks among the most outstanding in the oeuvre. The second register is the . He cuts a long signature, Bungo no Yukihira (豊後国行平作), on the toward the , the reverse of the general practice of his day; ordinary pieces survive, but only a few. The characters are scratched and artless, and in that clumsiness lies his individuality, for the Showa Meizukushi (正和銘尽), the oldest of the sword books, already records that forgeries of Yukihira abounded in the period and teaches that skillfully written characters are all false signatures (銘字の巧みなものは皆偽銘). His rare forms belong here too: a signed called notably well made; , exceptionally rare for his period; and a , few in his work, recorded in the Kozan .
Not all of these marks are his alone. The soft steel, the of the and the are named by the published sources as features common to the old work of Kyushu at large, Ko-Naminohira among them, and the imperial-collection texts trace that company to the classical style of the Shosoin treasures, faithfully transmitted. What sets Yukihira at its head is the union of the school features with his own: the under , the quiet with its small , the carvings at the , and the long on the . His fame is itself ancient, secure since the period, when the sword books already had to warn against his forgers; his carvings stand at the beginning of sword and anticipate the carving smiths of later centuries; and the Bungo tradition descends from his school.
Fujishiro rates him Sai-jo , and thirty-seven designated works stand on record, thirty-three of them signed. Two signed are handed down as in the imperial collection; ten blades are Important Cultural Properties; five are prewar Bijutsuhin, among them the Genkyu-dated once owned by Kujo Michihide and a formerly of Uesugi Kensho; and five blades hold the rank and fifteen the , twenty in the two tiers together. His blades passed in the Tokugawa shogun family and in the Mito and Kishu Tokugawa houses, and two carry of Koon dated 1 (1661). Even unsigned he is scarce: only four works stand among the designations, one a greatly shortened bearing the Yukihira agaru (行平上ル), another the of the Kishu Tokugawa family. The imperial and Cultural Property pieces are patrimony, resting in the imperial collection, in shrines and in long-held collections; what a collector may realistically encounter is the and tier, twenty blades, most of them signed of the classic manner. Such a blade comes to market only rarely, and the old caution of the Meizukushi keeps the question of the alive after seven centuries; when a with the scratched, artless long signature on the does appear, the intact above the , it carries a signature cut at the very dawn of the period in the smith's own hand.