Heianjō Nagayoshi (平安城長吉), together with Sanjō Yoshinori, stands as a representative swordsmith of Yamashiro Province in the Muromachi period. Sword-signature reference works record multiple generations bearing this name from the Nanbokuchō period onward, though no extant works appear to predate the early Muromachi era. The most representative smith of this lineage is identified as the one active around the Bunmei to Eishō-Daiei period, who maintained what the NBTHK describes as a relationship "by no means slight" with Sengo Muramasa of Ise Province. Since antiquity Muramasa has been regarded as having had a particularly close connection with the capital smiths, and Nagayoshi's works frequently display a Seki-style range closely resembling that of Muramasa. His oeuvre also reveals what the examiners characterize as a "private admiration" for the hitatsura approach of the earlier Hasebe line, the foremost pioneers of Kyoto.

Nagayoshi's working range is notably broad, encompassing katana, tantō, yari, and wakizashi. His forging typically presents tightly compacted ko-itame-hada with fine ji-nie and a tendency toward a whitish tone or shirake-utsuri. The hamon varies considerably across his output: works in calm suguha with ko-ashi and a bright nioiguchi recall earlier Yamashiro masters such as Rai Kunitoshi and Ryōkai; others display ko-notare mixed with ko-gunome in a gently undulating "wet-blade" temper with a tight, clear nioiguchi; deeply hardened gunome-midare mixed with chōji-like elements and strong ha-nie; and flamboyant hitatsura with muneyaki, tobiyaki, and vigorous sunagashi and kinsuji. A recurring observation across sessions is the tendency for the hamon on both sides to align, a feature shared with the Sengo group. His tantō characteristically exhibit a stocky form -- "although comparatively broad in width, they tend to be short in length." Nagayoshi was also widely recognized as an outstanding master of horimono, his carvings described as "truly splendid" and executed with "notable skill," particularly the distinctive kusa no kurikara in which the dragon's tail crossing the sword "appears as though it were raised in relief" -- a technique "scarcely to be confused with any hand other than Nagayoshi's."

Across more than six decades of Juyo sessions, the NBTHK consistently affirms Nagayoshi's standing as a figure of the first rank among Muromachi-period Kyoto smiths. His works are deemed "representative" of their era, and signed examples bearing the "Heianjō" prefix are regarded as "especially rare and the most highly prized," with craftsmanship considered "the most superior." The breadth of his productive range -- from classically elegant suguha recalling Kamakura-era Yamashiro masters to bold hitatsura in emulation of Hasebe -- is itself recognized as "valuable" for understanding the full measure of his technique.