At the second Tokubetsu Juyo session, in 1973, the NBTHK designated a suriage tachi signed Bishu ju Masahiro[[c:1]], recording it as the blade of this name whose ji and ha are of the finest workmanship[[c:2]]. Masahiro of Mihara in Bingo province stands with Masaie as one of the two representative smiths of Ko-Mihara, the collective name for the school's work from the end of Kamakura through Nanbokucho. "Masahiro is traditionally regarded as a son of Ko-Mihara Masaie"[[c:3]], in other texts a pupil, yet the same sources repeatedly invert the chronology: "judged from the workmanship, Masahiro reads older in style than Masaie"[[c:4]], several signed tachi being appraised as late Kamakura work. The name itself is collective. The signature references list six smiths called Masahiro in Bingo, the recorded dates opening in Joji 3 (1364) and running through Shitoku, Kakei and Oei, and "the Oei work is regarded as a second generation" (応永は二代とみられている). Extant dated blades are rare, only Shitoku and Oei examples being known, and the NBTHK treats the name collectively, several generations under one attribution.
His manner is Yamato carried into Bingo steel. Bingo held many estates of the central temples, Toji and the Rengeoin among them, and the published sources read the Mihara style as the product of that exchange: suguha-based work over a flowing itame. The same sources separate him from Yamato proper in one recurring formula: "compared with works from Yamato proper, the nie of ji and ha is as a rule weaker, the forging stands out in moku, the whitish utsuri is conspicuous, the hamon is a suguha whose nioiguchi tends to tightness, and the boshi turns back gently in a rounded manner"[[c:5]]. A pale shirake-utsuri rises in the ji on nearly half of his recorded works; his boshi runs straight to a gentle ko-maru return, often with hakikake, never to the yakizume that defines the Yamato schools; and his itame flows and stands without resolving into their full masame.
In detail the forging is itame mixed with moku and nagare-hada, standing in places, with very fine ji-nie, chikei entering finely, and patches of jifu. Over it the hamon is a medium suguha or suguha-cho mixed with ko-gunome and ko-midare, with ko-ashi and yo entering well; the habuchi frays into hotsure, kinsuji and sunagashi work through the ha, and the nioiguchi stays tight or subdued with thick ko-nie rather than bright heavy nie. The work divides into two registers. The signed tachi, mostly suriage though several keep their ubu nakago, carry the mei in large slender-chisel characters: the first generation signs invariably Bishu ju (備州住) and never Bingo no kuni ju, beside rarer three-character mei reading Masahiro saku (正広作) and two-character mei. The sanji-mei pieces read oldest; one tachi has its nakago recorded in the Ojakusho (往昔抄), the Muromachi compendium of sword rubbings. Beside them stands the o-suriage mumei register, katana attributed by kiwame, several settled by kinzogan attribution inscriptions rather than signatures; the Nanbokucho examples run wide in mihaba with o-kissaki, one of them "originally a tachi of nearly three shaku"[[c:6]].
Within the one suguha discipline distinct strains stand out. The tachi dated Shitoku 1 (1384), a 79.6 cm blade with its nagamei intact, keeps the suguha-cho base but takes nie throughout, yubashiri running hard along the upper half into niju and sanju-ba effects, and is singled out as "showing, within his oeuvre, a manner strong in the nie of ji and ha"[[c:7]]; a later designation links a sanji-mei tachi of the Nanbokucho end to it by the same yubashiri and nijuba. The Oei work, read as the second generation, leans toward the neighbors. The tachi dated Oei 6 (1399) shows "a manner that could at first sight be mistaken for the Rai school of Yamashiro" (一見山城国来派の作に見紛う作風), only the slight saki-zori betraying the period. The katana dated Oei 22 (1415), the one blade in the record signed Bingo no kuni ju Masahiro (備後国住正広), goes the other way toward Bitchu Aoe: a slanting lean enters the midare of its suguha, a midare-utsuri stands in the ji with jifu, and "the boshi burns its return deeply downward in waterfall fashion, the so-called Mihara-boshi" (帽子は返りを滝落し風に深く焼下げる所謂三原帽子となっている). A sun-nobi tanto of the same years lines up round-topped ko-gunome that the sources liken to the Hokke Kaneyasu (法華兼安) of the same province. The Aoe adjacency is old: the Muromachi treatise Shinkan Hidensho already wrote that the school's face "resembles a Bitchu tachi"[[c:8]].
Against Masaie, the school's other master, the record draws the kantei line through the ha. In Honma Junji's adjudication, "Masaie's hamon is almost invariably an orderly suguha, while Masahiro more often shows pieces with a degree of midare feeling and many activities within the ha"[[c:9]], the boshi likewise not uniformly round but at times tending to midare or nie-kuzure. The sugata divides the two as well: "Masaie has many works with o-kissaki, while Masahiro shows comparatively many with a moderate kissaki"[[c:10]]. The school's stream runs to the end of Muromachi, and the deep-returning boshi of his kiwame side is anchored by its celebrated blade, the meibutsu O-Mihara[[c:11]], a kinzogan-mei katana designated Important Cultural Property, invoked for the strikingly deep turnback seen within his work.
Fujishiro rates him Jo-jo saku. The official record carries thirty-seven designated works: one Important Cultural Property, the meibutsu O-Mihara itself, three Tokubetsu Juyo, twenty-five Juyo and eight Juyo Bijutsuhin, twenty-six of them signed against seven mumei, with four more carrying kinzogan attribution inscriptions. Seven blades hold recorded provenance, among them a Jubi tachi whose cut signature reads Bingo ju Masa (備後住正), passed from Prince Konoe Fumimaro to the Yomei Bunko, Kyoto, and another held by Asano Kii no Kami. The Important Cultural Property is patrimony, permanently held; recorded institutional holders are the Tokyo National Museum, the Tsukamoto Museum and the Yomei Bunko, the rest in private hands. For the collector the realistic field is the twenty-eight blades of the Tokubetsu Juyo and Juyo tiers: not beyond reach in the way the great Soshu and Bizen names are, but coming to market only from time to time. The signed tachi with the slender-chisel nagamei carry the chronology of the school; of one such the NBTHK closes its notice praising not only the work but the unforced, gentle character of the signature itself[[c:12]].
