Korekazu, by common name Masatarō, was the seventh-generation head of the Edo Ishidō line, the house that carried the Bizen chōji tradition into the capital and kept it alive through the Shinshintō revival of the nineteenth century. The published sources fix his biography in a nearly fixed formula repeated across his designation entries: he was a nephew of the Yonezawa domain smith Katō Chōunsai Tsunatoshi, learned forging first under Tsunatoshi, then married into and succeeded the sixth Ishidō Korekazu, and died in Meiji 24 (1891) at the age of seventy-five. His working life ran from the closing years of Tenpō into early Meiji, and comparatively many of his blades survive, nearly all of them signed and dated katana. He stands among the leading masters of the late Edo period; the published commentary ranks his skill alongside Jirōtarō Naokatsu and Hosokawa Masayoshi.
His hand is defined not by a motif but by a method, and the published sources state it the same way again and again. His works divide broadly into two modes, Bizen-den and Sōshū-den, but his true strength lay in the Bizen chōji that may be called the hereditary specialty of the Ishidō house. Where the other Shinshintō smiths working in the Bizen manner tempered their chōji in nioi-deki, Korekazu tempered his in nie-deki, and the commentary locates his originality precisely there, summing it up as the work of a smith popularly described as having "tempered Bizen-style chōji-midare in nie"[[c:1]], so that "in this one can discern his originality"[[c:2]]. Over a well-packed ko-itame he sets a chōji mixed with gunome, ko-chōji, ko-gunome and slightly pointed elements, the ashi entering long and frequently, the nioi deep, the nie thick with patches of coarser nie that leave the temper a little uneven, and through it run sunagashi and long kinsuji. It is a Bizen pattern carried on a Sōshū base, and the sunagashi threading nearly four of every five of his blades is the visible proof of it.
The jigane is the constant that underwrites the temper. His ko-itame is tightly forged, at times mixing flowing grain or mokume, the ji-nie laid in a dust-fine, thick cover with fine chikei entering frequently, and where the forging tightens hardest it approaches a muji-fū, near-featureless surface. The published sources single this forging out as especially strong even within his own work. The bōshi runs midare-komi to a ko-maru, often with hakikake at the tip and on his boldest pieces a flame-like sweep, and one entry notes that the handling of the bōshi betrays the mannerisms of his teacher Tsunatoshi, allowing a stylistic line to be drawn back to the older smith. The blades themselves are robust ubu katana, wide in body with thick kasane, the sori from shallow to deep and the point a long chū-kissaki or a generous ō-kissaki, the tang cut with bold ō-sujikai keshō file marks and a long six-character signature.
Within this one perfected manner the published sources read a style split rather than a sequence of periods. The Bizen nie-deki chōji is the core and the bulk of the record, and the judges call its finest examples the typical and outstanding work of the smith. The Sōshū-den register he himself claimed as a strength stands beside it: here the grain rises and flows rather than packs, and the temper turns toward ko-notare and gunome carried in nie with sunagashi, a manner allied to the Sōshū-leaning nie work fashionable in his day. The Ansei 2 (1855) daishō with its formal rō-nuri mounting and the Aizu collaboration with Kakuda-suke Gengō, where Gengō forged the blade and Korekazu set the temper, are its successes, the latter a sword the judges found to seem "entirely the work of Korekazu"[[c:3]]. A third, rarer face is the quiet one: on rare occasions he made suguha, and one Ansei 5 katana is singled out as comparatively gentle and restrained for him, a suguha-chō with gunome over a muji-fū jigane. Because all three share his deep-nioi, nie-deki temper, they read as one nie-based hand worked over different jigane rather than as opposed styles.
What sets Korekazu apart within the crowded Bizen revival is therefore not a feature but a technique, and the published sources are careful to draw the line the same way each time. Many Shinshintō smiths could reproduce the chōji-midare of old Bizen in nioi; Korekazu held the house chōji but forged it in nie, deep in nioi and thick in nie, with sunagashi, kinsuji and nie-suji working within the edge and a bright, clear nioiguchi. The link to Tsunatoshi is real and acknowledged in the bōshi, yet the nie-deki approach is his own departure from his teacher's tighter nioi-bound chōji. He is the smith who took the most academic of the Shinshintō programs, the literal copying of Kamakura Bizen, and made it personal by changing how the steel was hardened rather than what pattern it drew.
For the collector Korekazu is one of the more attainable of the major Shinshintō names, and his record should be read for what it is. Fujishiro grades him Jō saku, and the Tōkō Taikan values him at four hundred. He has no National Treasures and no Important Cultural Properties; his standing rests instead on the modern designation tiers, where roughly two dozen of his katana have reached the Jūyō rank across sessions spanning from 1964 to 2022, a steady presence that reflects how many sound, dated, signed works of his survive. The published commentary repeatedly calls his best the representative and typical work of the smith, and of one Jūyō katana it writes that it is "a blade in which the true specialty of Korekazu is brought forth without reservation, demonstrating an exceptionally distinguished workmanship"[[c:4]]. Among the recorded provenance is one blade held by the Imperial Family. His pieces also carry the texture of their late-Edo moment: one bears a carved slogan voicing the jōi ("expel the barbarians") sentiment of the day, and a Sanada-commissioned katana is inscribed in man'yōgana with the line "this tachi holds but one stored intent, to protect, indeed, for my lord"[[c:5]]. A signed, dated Korekazu katana comes to the serious collector with some regularity rather than as a once-in-a-lifetime event, and a well-made example in his hallmark nie-deki chōji is among the most rewarding ways to hold a piece of the Bizen tradition's final flowering.
