The Yoshioka school was a major branch of the lineage, flourishing from the late period into the era in Province. The tradition -- so called because its smiths incised the character "一" () into the tang -- had prospered through the period at Fukuoka, Yoshioka, and Iwato. As the earlier Fukuoka line waned, the Yoshioka branch rose to prominence, occupying a transitional position that carried the great mainstream forward into the fourteenth century. The school's principal craftsmen -- Sukemitsu, Sukeyoshi, Sukeshige, and Sukehide -- all share the generational element "" (助) in their names, a convention that marks their familial and artistic cohesion. Sukemitsu, who held the court title Sakonshōkan and left dated works spanning from the Einin through Gentoku eras, is regarded as the foremost smith of the group. A separate, earlier Fukuoka Sukesada (助貞), traditionally transmitted as the son of Sukezane, bridged the mid- Fukuoka tradition and the Yoshioka school's emergence, his workmanship closely resembling his father's brilliant manner.
The Yoshioka style is distinguished from the earlier Fukuoka by a shift toward more controlled, compact expression within the tempering tradition. Where the Fukuoka masters favored bold, large-patterned - of extravagant brilliance, the Yoshioka smiths developed a manner in which stands out conspicuously within the , the overall pattern somewhat smaller in scale yet no less refined. Across the school's members, the forging consistently presents mixed with , with very fine , abundant , and prominently standing -- the characteristic reflection effect of the tradition. The centers on mixed with , , and , with profuse and , fine , and touches of and . The is characteristically -dominant with , bright and clear -- a quality the singles out repeatedly as evidence of fine workmanship. Sukemitsu's tempering shows the most flamboyant expression, with marked undulations and height variation recalling the Fukuoka manner, while Sukeshige and Sukeyoshi tend toward more restrained variation, with areas of reverse-slanting tendency () or compacted quality () that the examiners identify as distinctive points of appreciation. Sukehide's works span both a serene mode and the school's characteristic , demonstrating the versatility that existed within the collective idiom.
Signed works by the Yoshioka smiths are universally described as exceedingly rare, and those retaining tang form with legible date inscriptions are especially prized as documentary evidence for the school's chronology. Sukeshige's blades bearing Enkyo and Sadawa-era dates attest to a working life spanning several decades, while Sukeyoshi's rare dated Gentoku 3 (1331) demonstrates a breadth of form unusual for smiths of this era. The consistently praises the school's output for refined and meticulous forging, bright , and the (sound and well-preserved) condition of both and . The Yoshioka school's enduring significance lies in its role as the principal vehicle through which the tradition was carried from the brilliant apogee of mid- into the expansive period, refining the inherited vocabulary into a more disciplined yet equally accomplished expression that represents one of the finest achievements of medieval Japanese swordsmithing.