Sadatsugu is an Aoe smith of Bicchu, working in the lower basin of the Takahashi River whose iron had been famous since the early-eleventh-century Shin Sarugakki listed "the swords of Bicchu" among the notable products of the provinces. The published sources call him "a representative smith of the Aoe forges"[[c:1]], placing him with the tsugu-signing masters of the line, a name that was carried on within the school down into the Nanbokuchō period. They are equally clear about the difficulty he presents: among works bearing the name there are signatures cut in a small manner, in an ordinary proportion, and in a somewhat later hand, so that "Sadatsugu is thought not to have been one man"[[c:2]]. His surviving signed blades are the spine of the record, and the one in the present catalogue is read, even within Ko-Aoe, as a work "of a somewhat later date"[[c:3]].

His characteristic hand is the tachi, shinogi-zukuri with iori-mune, deep in sori and finished with a chū-kissaki, the signature cut in two characters on the ha-ura near the nakago-jiri and toward the mune, the yasurime the steeply slanted ō-sujikai that marks a Bicchū tang. What distinguishes the work is not flamboyance but restraint: over the steel he sets a narrow suguha, the nioiguchi drawn tight and carrying ko-nie, into which only a measured ko-gunome and a little ashi enter, with tobiyaki appearing here and there toward the monouchi. It is the calm opposite of the towering clove-flower of mainstream Bizen, and the published sources name the orderly suguha with its suitably blended ko-gunome, set against the quality of the steel and a gentle bearing, "a piece that conveys the dignity of the Aoe school"[[c:4]].

The jigane is where the school speaks. On the signed tachi it is an itame mixed with mokume, inclining toward masame nearer the edge, with ji-nie adhering and jifu mixed through; on the shortened blade it tightens into a well-packed ko-itame with abundant ji-nie and chikei. Across both rises the Aoe jigane the published sources call "a jifu-toned utsuri"[[c:5]], the patchy reflection that stands in place of the clear midare-utsuri of Bizen and is the surest mark separating his steel from the otherwise comparable Bizen work. The bōshi runs straight to a small round, on the ura basically straight with hakikake and a somewhat long kaeri, and on the later blade a bō-hi is carved through.

What survives shows him in two registers of the one hand. The ubu, two-character signed tachi, with its small-style mei and ō-sujikai file marks, is his recognized type, quiet and orderly. Against it stands an ō-suriage blade whose long folded-back signature was, at some shortening, repaired and remade into an affixed inscription reading "Sadatsugu, resident of Bicchū Province"[[c:6]]; its multiple peg-holes show the blade was reduced more than once, yet the suguha and the fine ko-itame still carry the school's dignity. The variation in the manner of the signature across these works is exactly the evidence on which the published sources rest the conclusion that more than one smith used the name.

Within the Aoe line his hand sits beside the other tsugu-signing smiths, more subdued and astringent than the contemporary Bizen chōji. His own grounded tells set him apart: the jifu-toned utsuri in the steel, the narrow tight-nioiguchi suguha rather than a flamboyant midare, and the ō-sujikai file marks with the ha-ura two-character signature that the school cuts where Ko-Bizen would not. These, rather than any borrowed comparison, are what the published sources name as the basis of the Aoe attribution.

For the collector he is a scarce early Bicchū name. The Tōkō Taikan places him high, and his record is led not by the open market but by designated heritage: three of his blades are Important Cultural Properties, among them the signed tachi held by the Tokyo National Museum, a further signed tachi preserved in Toyama, and the kinzogan-attributed katana known as "Ō-Aoe," shortened and gold-inlaid with a Hon'ami appraisal. These are patrimony, held in museums and long-kept collections, and never come to market; one signed tachi of recorded whereabouts descended through the Kuroda house. Below them only a small number reach the Tokubetsu Jūyō and Jūyō tiers, so a signed Sadatsugu in private hands is among the rarer things a student of Ko-Aoe could hope to encounter, and one appears, when it does, only with patience.

Sadatsugu is an Aoe smith of Bicchu, working in the lower basin of the Takahashi River whose iron had been famous since the early-eleventh-century Shin Sarugakki listed "the swords of Bicchu" among the notable products of the provinces. The published sources call him "a representative smith of the Aoe forges"[[c:1]], placing him with the tsugu-signing masters of the line, a name that was carried on within the school down into the Nanbokuchō period. They are equally clear about the difficulty he presents: among works bearing the name there are signatures cut in a small manner, in an ordinary proportion, and in a somewhat later hand, so that "Sadatsugu is thought not to have been one man"[[c:2]]. His surviving signed blades are the spine of the record, and the one in the present catalogue is read, even within Ko-Aoe, as a work "of a somewhat later date"[[c:3]].

His characteristic hand is the tachi, shinogi-zukuri with iori-mune, deep in sori and finished with a chū-kissaki, the signature cut in two characters on the ha-ura near the nakago-jiri and toward the mune, the yasurime the steeply slanted ō-sujikai that marks a Bicchū tang. What distinguishes the work is not flamboyance but restraint: over the steel he sets a narrow suguha, the nioiguchi drawn tight and carrying ko-nie, into which only a measured ko-gunome and a little ashi enter, with tobiyaki appearing here and there toward the monouchi. It is the calm opposite of the towering clove-flower of mainstream Bizen, and the published sources name the orderly suguha with its suitably blended ko-gunome, set against the quality of the steel and a gentle bearing, "a piece that conveys the dignity of the Aoe school"[[c:4]].

The jigane is where the school speaks. On the signed tachi it is an itame mixed with mokume, inclining toward masame nearer the edge, with ji-nie adhering and jifu mixed through; on the shortened blade it tightens into a well-packed ko-itame with abundant ji-nie and chikei. Across both rises the Aoe jigane the published sources call "a jifu-toned utsuri"[[c:5]], the patchy reflection that stands in place of the clear midare-utsuri of Bizen and is the surest mark separating his steel from the otherwise comparable Bizen work. The bōshi runs straight to a small round, on the ura basically straight with hakikake and a somewhat long kaeri, and on the later blade a bō-hi is carved through.

What survives shows him in two registers of the one hand. The ubu, two-character signed tachi, with its small-style mei and ō-sujikai file marks, is his recognized type, quiet and orderly. Against it stands an ō-suriage blade whose long folded-back signature was, at some shortening, repaired and remade into an affixed inscription reading "Sadatsugu, resident of Bicchū Province"[[c:6]]; its multiple peg-holes show the blade was reduced more than once, yet the suguha and the fine ko-itame still carry the school's dignity. The variation in the manner of the signature across these works is exactly the evidence on which the published sources rest the conclusion that more than one smith used the name.

Within the Aoe line his hand sits beside the other tsugu-signing smiths, more subdued and astringent than the contemporary Bizen chōji. His own grounded tells set him apart: the jifu-toned utsuri in the steel, the narrow tight-nioiguchi suguha rather than a flamboyant midare, and the ō-sujikai file marks with the ha-ura two-character signature that the school cuts where Ko-Bizen would not. These, rather than any borrowed comparison, are what the published sources name as the basis of the Aoe attribution.

For the collector he is a scarce early Bicchū name. The Tōkō Taikan places him high, and his record is led not by the open market but by designated heritage: three of his blades are Important Cultural Properties, among them the signed tachi held by the Tokyo National Museum, a further signed tachi preserved in Toyama, and the kinzogan-attributed katana known as "Ō-Aoe," shortened and gold-inlaid with a Hon'ami appraisal. These are patrimony, held in museums and long-kept collections, and never come to market; one signed tachi of recorded whereabouts descended through the Kuroda house. Below them only a small number reach the Tokubetsu Jūyō and Jūyō tiers, so a signed Sadatsugu in private hands is among the rarer things a student of Ko-Aoe could hope to encounter, and one appears, when it does, only with patience.