Hiroyuki is a smith of the school, the lineage, working in the mid- period around the Shohei era, and transmitted as a son of Yukihiro. He belongs to the group of followers the published sources call Sue-, the smiths carried on from O- after the school's founder. The school emerged in the early and broke decisively with the older Kyushu manner, in which the and are subdued and rustic in a restrained ; drawing on the tradition it established a style in which both and are bright and clear, with and intermingled. Hiroyuki worked within that style, and his place is fixed by the few dated and signed records the swordbooks preserve: a work said to bear a Shohei 20 date of 1365, against his father Yukihiro's piece of the Koan years. Signed work by his hand is extremely rare, so almost his whole surviving record is the , attributed to him from long later shortened.
His recognized hand is read most clearly in the temper. Over a wide, shallow-curved blade he forges a line based on that carries a shallow , into which , angular , , pointed and enter, often in a continuous, linked succession kept comparatively small in scale. The lies thick and uneven, with coarse gathering in clusters, uchi-noke and touching the edge, and and running vigorously through it, the often taking a subdued, cast. What the published sources name as his tell is precisely this manner: among the group, whose hands are so closely matched that the individual smith is hard to single out, it is the blade whose stands out and runs continuously, and whose temper is comparatively restrained, the rises and falls not standing out strongly, that is read as Hiroyuki. Several of his entries close on the judgment, that the work is the one 「弘行に最も擬せられるものであり」, most readily likened to Hiroyuki.
The is the constant beneath both faces of his work. He forges a standing mixed with and flowing grain, with patches of large in places, thickly covered in , entering well, the steel taking a somewhat blackish, whitish-misty cast. This is the -derived , an open, -laden steel rather than the bright, tightly packed with its clear ; where a reflection appears at all it is only a faint or a whitish tendency. Beside the -prominent line the published sources read a quieter register of the hand, a with only a shallow , and angular elements entering sparingly, the pattern small, fine along the , and the subdued. The in his bolder work runs , thrusts up and ends pointed with vigorous ; in the calmer register it runs straight to a .
The two registers answer to how the blade was authenticated. The bold, -prominent carry the school's spirited character, one described as a 「放胆で覇気に溢れた出来口」, a bold and spirited workmanship. The quieter pieces, several bearing gold-powder attributions added by the house, show the wide with and the subdued the appraisers long read as Hiroyuki. The published sources are candid about the limits of this judgment. They class him among the Sue-, of whom they say that 「作風を区別することは困難である」, that distinguishing the styles of the individual smiths is difficult, and they note that the gold-powder attributions seen on his blades are a Meiji-and-later practice begun by the family. Of one such piece they grant openly that there is a question 「左弘行とまで断定し得るか否か」, whether it can be fixed conclusively as Hiroyuki, while affirming that 「南北朝期の左の一派の作であることには異論がない」, that there is no dissent it is the work of the school.
What sets Hiroyuki apart is therefore a matter of degree within a closely matched school rather than a private signature. His own evidenced tells, the continuous in a small-patterned, -leaning temper, the standing with its blackish -laden steel, and the thrusting, pointed , place him beside Yasuyoshi, Yukihiro, Yoshisada, Kunihiro, Hiroyasu and Sadayoshi, the Sue- hands carried on from O-. The published sources hold his skill within that company and affirm his attributions from era and school, naming his comparatively calm, -leaning manner as the side of the tradition that bears his name. He stands one generation below the founder, working the grand form in the school's bright, -rich idiom rather than reaching for the flamboyance of its first masters.
For the collector Hiroyuki is a documented name carried at the higher modern designation tiers. Fujishiro grades him Jo . His record runs through two , one of them carrying a Ringa gold-powder , two prewar Bijutsuhin, and some twenty-nine blades at the rank, thirty-one in the and tiers together. His blades are rooted in provenance, the Ii family of Hikone, whose -ni-tachibana mounting accompanies one , and the Nabeshima family, with further pieces passing through the Tsuchiya house of Tsuchiura and the Tokugawa, and one preserved in a municipal museum collection. Because almost his entire record is and held in long-standing collections, a Hiroyuki seldom comes to market; when one does appear it is from the and tiers, and the patient collector may encounter such a blade from time to time, a sound and forceful document of how the school carried its bright manner into the second generation.