A dated Shohei 17 (1362) and signed Choshu ju Yasuyoshi, today a , anchors nearly everything the published sources say about Yasuyoshi of . Its hand is identical to his customary signature, and on that identity rests the account repeated at the head of entry after entry: Yasuyoshi was the son of O- (大左), succeeded him as the second generation of the line, and later moved from to Nagato. His dated work runs from Shohei 17 into the era, and an Important Cultural Property signed Yasuyoshi is catalogued with the earlier date Shohei 12 (1357). The name did not end with him, for descendants or pupils carried it in Nagato into the early period, the line the sources call Choshu- (長州左). Across half a century of designations the assigns him one constant character, stated in almost the same words each time: his is the work in which, "within the family a temperament intermingles".
The signed record has a strict shape. Every signed Yasuyoshi the published sources describe is a or in , most of them wide and , thin in and shallow in , the full mid- stance; where O-'s stay small, his mostly run large. The published sources state plainly that no authenticated signed exists, so the and in their pages survive as attributions. One Important Cultural Property , held at Shirasaki Hachimangu in Yamaguchi, is nonetheless catalogued as signed Yasuyoshi, known so far only from its brief plate. The itself is a large two-character signature cut with a somewhat thick chisel below the at the center of the . On occasion it is prefixed with the character , a form headed by the Hitotsuyanagi Yasuyoshi (一柳安吉), an Important Cultural Property. The record is just as exact about an absence: works signed Yasuyoshi (左安吉) and Choshu ju Yasuyoshi both survive, but "one does not see examples signed Chikushu ju Yasuyoshi".
His is an that flows and often stands, mixed with , with attached. Over it rises a whitish , a , or a near the edge, and the published sources name this flowing, standing forging with its whitish cast the viewing point of the smith. The is a shallow mixed with , and pointed elements, -dominant with . enter, fine runs through, and appear here and there. The runs or thrusts up in fashion, leans slightly toward the edge, and ends pointed with light and a rather long return. Set against his father the judgment is plain: the brilliance of and falls short of O-, one early entry stating without ceremony that "his skill as well does not reach his father", and the , lacking O-'s sharpness, often falls into a leaning tendency. These same qualities form the stated trap. -dominant with set in, his work "at first sight strays among pieces such as Kanemitsu", and the standing only strengthens the impression.
Two registers complicate the portrait at its edges. A minority of his smallest , nearly O-'s own size with a slightly withered , keep close to the master: dust-fine thick , fine , at times a , a bright clear with and sweeping through, the pointed, a make the published sources call "truly mistakable for O-". On the signed Yasuyoshi, the character is fluent and close to O-'s own hand while the two characters of Yasuyoshi show a somewhat naive chisel; whether such pieces prove the tradition that O- himself signed Yasuyoshi in his last years, or are instead Yasuyoshi's earliest work, the leaves open for future study. At the other edge stand the Nagato years. The Nagato-signed work takes more strongly than his usual -dominant hand. On a the published sources call one manner of the Choshu Yasuyoshi, and take strongly, the grows bold with mixing in, sweeps with entering, and the thrusts up to a point. Oei-dated work is judged plainly a successor generation, while the Eiwa-dated pieces stand unresolved between the founder's last years and a second generation, a question the published sources repeat as a subject for future research.
On unsigned blades of the type his own marks decide the attribution. Where the flowing, standing carries a whitish , where the temper turns -dominant in small patterns, and where the thrusting pointed softens into a lean, the work is likened to Yasuyoshi within the school, and several have been so appraised. The pointed is the -family inheritance he never gives up; the softness of the edge is his own. The recent entries single out "the deep carrying a soft feeling" and the rich activity working inside the , finding in them a strength that remains his even where the brilliance does not match his father's.
Fujishiro rates him Jo-jo , and the record is unusually legible: forty-two designated works are on record, thirty-four of them signed against seven unsigned. Six blades are Important Cultural Properties, headed by the Hitotsuyanagi Yasuyoshi; four are , among them the dated Shohei 17 ; and thirty-one stand in the and tiers, one praised as "the very finest within this smith's work". Twelve blades carry recorded provenance: examples passed in the Ikeda and Inshu Ikeda houses, the Tosa Yamauchi and the Maeda, one certified in the ownership of Tokugawa Iesato, and another treasured by Motoda Nagazane, the Confucian scholar of Kumamoto. Of recorded whereabouts today, blades rest in the Tokugawa Art Museum, the Fukuoka City Museum, the Tokyo National Museum and the Sano Art Museum. The Important Cultural Properties are patrimony and will remain where they are; much of the rest is held by institutions or in long private keeping, and a signed Yasuyoshi coming into open hands is an uncommon event, appearing only rarely and rewarding patience.