Sadayoshi is a smith of the Chikuzen Sa school, the line of Samonji, working in the middle of the Nanbokuchō period. The published sources place him among the Sue-Sa, the second wave of pupils who carried the school forward after Ō-Sa: "Sadayoshi is said to have been the son of Yasuyoshi and is traditionally placed among the smiths active around the Bunna era"[[c:1]]. Yasuyoshi was himself a son of Samonji, so Sadayoshi sits two generations down from the founder, in the company the commentary names together time and again, Yasuyoshi, Yukihiro, Yoshisada, Kunihiro, Hiroyuki, Hiroyasu and Sadayoshi. The Chikuzen Sa school had emerged in the early Nanbokuchō and broken decisively from the older, classical Kyūshū manner, establishing a new style in which both jigane and hamon are bright and clear and in which chikei and kinsuji stand out; Sadayoshi is one of the heirs who forged in that idiom.
The central fact of his record is its near-total reliance on attribution. The published sources state plainly that "extant signed works are extremely few"[[c:2]], and almost everything that survives under his name is the ō-suriage, mumei katana judged to him. What allows the judges to single him out of the school is one feature, and the commentary names it without hesitation: a calm, suguha-based temper. They observe that "among unsigned blades appraised to the Sa group, one frequently encounters pieces whose tempering is founded on suguha"[[c:3]], and it is this restrained manner, long held the key point in appraising his work, that resolves a Sa-group blade specifically to Sadayoshi. On one katana the appraisal is put as simply as it can be, that "because the overall impression is comparatively gentle and quiet, it is reasonable to determine the attribution to Sadayoshi"[[c:4]].
The jigane is the Sōshū-derived steel he shares with the whole Sa line. He forges a standing itame, mixed with mokume and a flowing nagare-hada, the grain conspicuous and at times opening; over it the ji-nie lies thick and the chikei enter frequently, the steel inclining at times toward a dark tone, and on several blades a faint, whitish utsuri rises along the shinogi. Above the jigane the temper is a wide suguha or chū-suguha with a shallow notare, into which a little gunome and ko-gunome are mixed; ashi and yō enter, kinsuji and sunagashi run, the nie gathers thickly, and the nioiguchi at times tends to subside. The bōshi is the school's constant and his most reliable structural tell, rising with a thrusting tsukiage tendency to a sharply pointed tip and swept with hakikake, the feature the judges repeatedly call typical of the Sa lineage. A bō-hi is generally carved through.
Within that one suguha-led manner the attributions divide into a quieter and a more animated register. At its calmest the line is a wide suguha barely undulating, the activity carried in ashi and yō and in fine kinsuji rather than in any tall pattern. In a number of blades the same foundation opens out: the yakihaba widens, the line takes a ko-notare with gunome and angular elements, the nie thickens and grows uneven with coarser grains, hotsure frays the edge, uchi-noke and a nijūba-like doubling appear, and yubashiri or small tobiyaki collect near the monouchi. Even at its most active the body of the temper stays suguha, and the pointed, swept bōshi holds, so the reading remains Sa-group work given to Sadayoshi. The published sources judge several of these especially well made among works attributed to the smith, the broad yakihaba and abundant nie lending a powerful, splendid impression in concert with the bold Nanbokuchō shape. The blades are wide-bodied with little taper and an extended chū-kissaki or ō-kissaki, several refashioned from naginata, and a handful carry a later cutting inscription in gold inlay or, in one case, only a red-lacquer character on the tang, which the judges read not as the founder's name in the narrow sense but as a mark of the Sa group as a whole.
What distinguishes Sadayoshi within his own school is exactly the thing that makes him hard to find. The commentary reads the Sa group as a line of comparatively few individual features, the smiths so close in hand that their unsigned work is hard to separate; against that, his calm suguha and his pointed, swept bōshi are what carry a blade to his name rather than to a brother's. His bright, chikei-laden jigane and the suguha-toned edge set him apart from the more flamboyant gunome and notare of the wider Sa circle, and his is read as the quiet, classical face of the late school, the manner in which the Sōshū inheritance is held in restraint.
Fujishiro grades Sadayoshi Jō-jō saku, and his standing in the Tōkō Taikan is recorded at the middle rank. He has no National Treasures, and his record runs entirely through the modern designation tiers: a substantial body of his attributed katana, more than twenty, has reached the Jūyō rank across more than a dozen sessions of shinsa, several of them judged especially fine among works given to the smith. Provenance is thin in the published record; of recorded whereabouts one blade is held by the Kurokawa Institute of Ancient Cultures, the rest passing through private hands. Because a reliably signed Sadayoshi is among the rarest things in the late Sa record, the collector encounters him almost always through these unsigned, shortened katana, and even those come to market only from time to time and with patience. A blade securely papered as Sa Sadayoshi is not beyond reach in the way a National Treasure is, but it is a quiet, considered acquisition, valued less for a famous name than for the calm suguha hand by which the judges still know him.
