A dated Bunkyū 2 (1862), made in his forty-fifth year, is singled out by the published sources as an especially outstanding blade in the manner he favoured, the clarity of both and splendid. Its maker, Ishidō Unju Korekazu, was born in Yonezawa in Dewa and known by the common name Masatarō. He was a nephew of the Yonezawa domain smith Katō Chōunsai Tsunatoshi and first learned forging under him. He then became the son-in-law of the sixth Ishidō Korekazu and succeeded as the seventh head of the Ishidō house, dying 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 works survive. The published commentary counts him among the leading masters of the period, standing shoulder to shoulder in skill with Jirōtarō Naokatsu and Hosokawa Masayoshi.
The published sources describe his hand through a method rather than a motif, and they state it in nearly the same words entry after entry. His work divides broadly into two modes, - and , but his true forte was the that may be called the hereditary specialty of the Ishidō house. Whereas many smiths working in the manner tempered their in , Korekazu tempered his in , and the commentary concludes that "in this one can discern his originality". Two entries put the reputation in a phrase: he is the smith described as having "tempered -style in ". One entry also gives the development behind it. His early works, like those of his teacher Tsunatoshi, show a tight and a with ; in later years he tempered this in small , which the source says brought a further degree of variation into the .
On the typical blade the is mixed with , , and slightly pointed elements. The enter long and frequently, the is deep, and the lies thick, with patches of coarser that leave the temper a little uneven. runs through the on about three of every four of his blades, often joined by and , and the is bright and clear. The is a tightly forged , at times mixed with or flowing grain. Its lies in a fine, thick cover with fine entering frequently, and where it packs hardest it approaches a - surface. One entry singles out this forging as especially strong even within his own work. The runs to a , often with , and one entry finds in its handling the mannerisms of Tsunatoshi, from which it infers a stylistic tie between the two smiths. The blades are robust , wide in body with thick , the point a long or an , the tang finished with file marks and a long signature.
Beside this core the published sources record other registers. Korekazu, one entry notes, himself claimed a proficiency in , though most of his finest works are . A of Ansei 2 (1855) succeeds in the manner and comes with a formal rō-nuri mounting whose full set of fittings is by Yokoya Sōju. A with the Aizu smith Kakuda- Gengō, his exact contemporary, records that Gengō forged the blade and Korekazu applied the temper; the judges found that it seems "entirely the work of Korekazu". The rarest face is . A long, robust of Ansei 5 (1858) over a - forging carries a -based temper with , deep in with a bright , and the source calls it "a comparatively gentle style" for him.
The record keeps returning to the same blades as his measure. Of one , whose carries dust-fine thick and whose temper shows and with unusual vigour, the commentary writes that it is "a blade in which the true specialty of Korekazu is brought forth without reservation, demonstrating an exceptionally distinguished workmanship". Other long blades with are praised for holding together without strain despite their length. His work also carries the marks of its moment. One is carved with the characters printed in the source as 「譲夷」, a carving the entry reads as showing the temper of the age. Another was made for Sanada Kōkan, a retainer of the Sendai Date house, and its tang carries a verse in man'yōgana: 「この太刀に貯めし心は身一つよ、守るたまかは我が君のため」 ("the heart I have stored in this is but one: to protect, indeed, for my lord").
Fujishiro grades him Jō , and the Tōkō Taikan values him at four hundred. He has no National Treasure and no Important Cultural Property. Twenty-four of his are designated , at sessions from 1964 to 2022, and a twenty-fifth, a dated Kaei 6 (1853), is recorded in Honma's inventory of the Imperial collection. That entry adds a note of regret: his was the era of the Meiji sword ban, and "it is regrettable that he could not fully exercise his skill". All of these blades are signed, and most are dated. Because comparatively many survive, a signed, dated Korekazu comes to market from time to time rather than once in a generation, and a sound example in his is among the more attainable ways to hold the late revival at its most personal.