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 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 records the published sources preserve: a work of his said to bear a Shohei 20 date of 1365, against his father Yukihiro's piece dated Kan'o 1, in 1350. 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 tempers a line based on that carries a shallow , into which , angular , , pointed and enter, often in a linked succession kept comparatively small in scale. The lies thick and uneven, with coarse gathering in places, uchi-noke and touching the edge, and and running vigorously through it. The often takes a subdued, cast. The published sources name this manner as his tell. Among the group, whose hands are so closely matched that the individual smith is hard to single out, the blade whose stands out and runs continuously, and whose temper is comparatively restrained, is the one read as Hiroyuki. Several of his entries close on the same 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 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; 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 same hand: a with a shallow , and angular elements entering sparingly, fine along the , and a subdued . The is the most constant feature of all. On most of his blades its tip ends pointed, whether it runs or nearly straight, often with vigorous . The outright upward thrust of is named on only a minority of them, and a few run straight or in a shallow to a . The published sources name the pointed, brushed among the traits that mark his work as .
The two registers answer to how the blade was authenticated. The bold, -prominent carry the school's spirited character, one described as 「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 「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. They note that the gold-powder attributions on his blades are a practice begun by the family in the Meiji era and after. Of one such piece they grant that there is a question 「左弘行とまで断定し得るか否か」, whether it can be fixed 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 are the continuous in a small-patterned, -leaning temper, the standing with its blackish, -laden steel, and the pointed, brushed . They place him beside Yasuyoshi, Yukihiro, Yoshisada, Kunihiro, Hiroyasu and Sadayoshi, the pupils who carried on the founder's manner. The published sources 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.
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 gold-powder by Ringa, two prewar , and twenty-nine blades at the rank, thirty-one in the and tiers together. His blades are rooted in provenance. One is accompanied by a mounting bearing the -ni-tachibana crest of the Ii family of Hikone, and further pieces passed through the Nabeshima family, the Tsuchiya house of Tsuchiura and the Tokugawa, with one held in the Tsuchiura City Museum. 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 meet such a blade from time to time, a sound and forceful document of how the school carried its bright manner into the second generation.