Mutsu no Kami Tadayoshi is the third generation of the Hizen main line at Saga, the eldest son of the second-generation Ōmi no Daijō Tadahiro. Born in Kan'ei 14 and called Shinzaburō, he received the title Mutsu no Daijō in Manji 3, became Mutsu no Kami in Kanbun 1, and died in Jōkyō 3 at fifty, seven years before his father. The Tadayoshi name came to him because, after the death of Tosa no Kami Tadayoshi, that house returned it to the main line. The published sources explain the comparative scarcity of his work by a short career and by his service for his long-lived father, his works being few "because he served as a substitute maker for his father"[[c:1]].
His characteristic manner is a chū-suguha, the temper the published sources call the one "he most excelled in"[[c:2]]. It is tempered with deep nioi and well-adhered ko-nie, small ashi entering, fine kinsuji and sunagashi running through it, and a bright, clear nioiguchi. The sugata is typically long, wide and thick, with a deep sori and an extended chū-kissaki, heavy in the hand. The judges read this shape as his grandfather's rather than his father's, "calling to mind not the father but rather the grandfather, the first-generation Tadayoshi"[[c:3]]. The bōshi is a ko-maru that turns back deeply and stops firmly toward the mune, and the published sources single this out: "the ko-maru of the bōshi is deeper than in the first and second generations"[[c:4]].
His reputation rests above all on the jigane. A ko-itame packed tightly, with ji-nie fine and thick, takes on the rice-bran komenuka-hada of Hizen, and chikei enter finely to give it strength. The published sources call his forging "the strongest and most refined of the upper three generations"[[c:5]] and name it his true hallmark, "the excellence of his forging is his true hallmark"[[c:6]]. On one Tokubetsu Jūyō katana they go further, finding the fine activity of a suguha edge "to the degree of surpassing the first generation"[[c:7]].
The record falls into distinct groups that the published sources themselves draw. An early group is placed by the shape of the nakago tip, judged "an early work of this smith from the iriyamagata tip and the manner of signature"[[c:8]]; even these already show the strong jigane and the deep bōshi. Beside the suguha stands a chōji-midare register. His own chōji mixes gunome, angular and pointed elements, small in pattern and with some rise and fall, and "small tobiyaki at the heads are often seen"[[c:9]]. On some wakizashi he tempered his father's ashinaga-chōji, and on one tachi the pattern is "to be mistaken for the chōji-midare of his father Ōmi"[[c:10]]. Dated works are scarce: the published sources state that "dated works by this smith are extremely rare"[[c:11]], and they treat his Kanbun 2 and Enpō 4 blades as documents of his signature.
Part of his record carries his father's name. Five blades signed Hizen no Kuni ju Ōmi no Daijō Fujiwara Tadahiro are judged by the NBTHK to be his work, each concluding that "this sword is perceived to be a substitute work of the third-generation Tadayoshi"[[c:12]]. The evidence is his own hand: a chōji smaller and livelier than the father's orderly ashinaga-chōji, ji-nie finer and thicker with more prominent chikei, a deeper bōshi, shallow katte-agari file marks and the chisel of the signature. The published sources value them as material "for knowing the work of the third generation as substitute maker for his father the second-generation Tadahiro"[[c:13]]. He is also the maker of a rare gassaku with the second-generation Masahiro, which the published sources call unique: "a joint work of the third-generation Tadayoshi and Masahiro is not seen apart from this sword"[[c:14]].
Two further judgments shape his record. A rare katana signed only with the five characters Hizen no Kuni Tadayoshi is attributed to him rather than to the founder, by the chisel of the signature, the position of the mekugi-ana and the workmanship; the published sources note that "the five-character Tadayoshi signature of this smith is extremely rare"[[c:15]]. They also caution that the main line signs katana on the ura in the tachi-mei position, so that a signature in the katana-mei position "calls for particular care regarding authenticity"[[c:16]].
Fujishiro grades him Jō-jō saku. He has no National Treasures or Important Cultural Properties on record; his standing rests on nine blades in the Tokubetsu Jūyō rank and some fifty in the Jūyō, with two blades in the Imperial collection. Several of the Tokubetsu Jūyō katana are called his finest workmanship, one of them "transmitted in the Nabeshima family in the domain era"[[c:17]], the house his line served. Signed blades of Mutsu no Kami survive in real numbers and a Jūyō example reaches the market from time to time, while his finest komenuka suguha katana come to light only rarely and are a landmark when they do.