Nobukuni represents a distinguished lineage among the Kyoto smiths (kyo-kaji) that flourished from the Nanbokucho period through the Muromachi period. The first-generation Nobukuni belonged to the Ryokai line of swordsmiths, and tradition holds that he studied under Soshu Sadamune of Sagami. Some accounts further record that he was either a son or grandson of Ryokunobu. Extant works bearing dates from the Enbun, Koan, and Joji eras are attributed to the first generation. Thereafter, toward the close of the Nanbokucho period, a succeeding generation of Nobukuni is recognized, with dated works from the Eitoku, Shitoku, and Meitoku eras. Notably, a blade dated Meitoku 3 exists alongside another of the same year signed "Genzaemon no Jo Nobukuni," indicating that even within the Nanbokucho period multiple smiths worked under the Nobukuni name. Upon entering the early Muromachi period, the so-called Oei Nobukuni appeared, notably Saemon no Jo Nobukuni and Shikibu no Jo Nobukuni.

Across the successive generations, Nobukuni workmanship divides into two principal modes: a suguha reflecting the ancestral Rai tradition of Kyoto, and a notare-dominant temper inheriting a Sadamune-like manner. From the late-Nanbokucho successor generation through the Oei-period Nobukuni, one can further observe a working range featuring midare-ba in which gunome predominates. In the suguha mode, the nioiguchi tends toward shimaru and is vividly clear and bright, with ko-nie construction, kinsuji, sunagashi, and streak-like nie-utsuri manifesting the refined character of Kyoto work. In the gunome-based midare, a distinctive tempering conception emerges in which pairs of gunome are linked by low, small notare lines, creating a brilliant, animated irregularity. The nioi is characteristically deep, with thickly adhering ko-nie, and in places somewhat coarse nie is intermingled; yubashiri and muneyaki appear, while sunagashi and kinsuji work effectively throughout, yielding a bright and clear nioiguchi. The forging typically shows itame-hada mixed with mokume and flowing grain, with abundant ji-nie and conspicuous chikei. Blade carvings are a hereditary specialty of the school, executed with notable skill across bonji, suken, gomabashi, and elaborate Buddhist iconography on both omote and ura.

Nobukuni occupies a position of particular significance among the Yamashiro smiths of the Nanbokucho period as a lineage that absorbed Soshu influence while preserving the traditional Kyoto manner. The range of extant work -- from tachi of considerable length and dignified presence to compact and well-proportioned ken and tanto in hira-zukuri -- demonstrates the school's versatility across form types. Signed tachi are comparatively few, making such examples especially valued. Among the appraised works, the manner in which rounded-headed gunome link and undulate is recognized as a decisive feature for attribution, while the suguha pieces faithfully demonstrate continuity with the ancestral Rai tradition. Many surviving blades are praised as kenzen -- sound and well-preserved in both ji and ha -- with ample niku-oki, attesting to the enduring quality of the school's craftsmanship across multiple generations of work.