Yasuyoshi, the son of O-Sa, succeeded as the second generation of the Sa lineage and is traditionally said to have moved from Chikuzen to Choshu (Nagato Province). This account is supported by an extant tanto dated Shohei 17 (1362) bearing the inscription "Choshu-ju Yasuyoshi," whose manner of signing matches his usual style. Subsequent works explicitly stating "Choshu Yasuyoshi" include examples dated to the Eiwa and Oei eras. The Oei-dated pieces are judged to be by a successor generation on the basis of workmanship and signature style, while whether the Eiwa-dated works represent late production by the first generation or early work by a successor remains a subject for future research. Descendants and students continued the Yasuyoshi name for several generations from the late Nanbokucho through the early Muromachi period, collectively known as "Choshu Sa."

In the forge, Yasuyoshi's work typically displays itame-hada mixed with mokume and nagare-hada, with the grain sometimes standing and ji-nie adhering. A whitish shirake-utsuri is a hallmark of the school, and tightly forged pieces show extremely fine ji-nie with delicate chikei and clear steel. The hamon most characteristically takes the form of shallow ko-notare mixed with gunome, with ashi entering and a nioiguchi that is bright and clear. The temper is primarily nioi-dominant with ko-nie, accompanied by fine kinsuji and sunagashi. The boshi typically enters in midare-komi with a pointed tendency and a long kaeri. Compared with O-Sa, the setsumei consistently note that Yasuyoshi's work does not exhibit the same degree of brilliance in both jigane and temper, though certain pieces with strong nie and kuichigai-ba demonstrate a broader range within his oeuvre.

Yasuyoshi's blades are generally of larger and more imposing sugata than those of his father, with wide mihaba and thin kasane. Among his finer works, the forging is well-refined and compact, with the Sa school's characteristic features clearly retained. Pieces of distinguished provenance, including examples transmitted in the Inshu Ikeda and Maeda collections, attest to the esteem in which his work has long been held.