Nobufusa is one of the earliest identifiable smiths of the Ko-Bizen tradition, active during the late Heian to early Kamakura period in Bizen Province. His precise genealogical position has long been a subject of scholarly debate: reference meikan list smiths bearing the name Nobufusa under both the Ko-Bizen and Ko-Ichimonji lineages, and one theory holds that the Ko-Ichimonji Nobufusa — said to have been among Emperor Go-Toba's goban kaji — was the same individual or a direct descendant. To distinguish the two, older scholarship refers to the earlier figure as "En-Nobufusa" and the later as "Shin-Nobufusa." A traditional convention assigns the two-character mei "Nobufusa" to the Ko-Bizen smith and the three-character mei "Nobufusa saku" to the Ko-Ichimonji smith, though Honma Junji challenged this division in the Nihonto Bunrui Mokuroku, reclassifying the three-character works under Ko-Bizen on the basis of workmanship alone. Whether one or two individuals are represented remains an open question, but the surviving body of work is unified by a distinctly archaic character that places it firmly within the oldest stratum of Bizen production.

Nobufusa's blades are marked by a classic Ko-Bizen sugata: slender proportions with pronounced funbari, high koshizori that shifts toward a fukusari tendency near the upper body, and a compact ko-kissaki. The jigane is typically an itame-hada — at times tending toward ko-itame mixed with mokume — into which thick ji-nie settles and fine chikei work through the steel; midare-utsuri stands distinctly across the surface, and occasional jifu-like mottling adds depth to the ground metal. The hamon is characteristically restrained: a suguha-based temper mixed with ko-midare and ko-choji, accompanied by frequent ashi and yo. The nie is deep and well-adhering, with kinsuji and sunagashi appearing throughout. Several signed examples exhibit yakiotoshi at the base. The boshi is typically sugu with ko-maru, occasionally showing hakikake. Surviving ubu tangs display the distinctive kijimomo-gata form with katte-sagari file marks, and the signatures — whether in two or three characters — are cut in a large, unaffected hand that itself carries an antique flavor.

Nobufusa's importance extends beyond technical accomplishment. The celebrated tachi known as Jumansoku ("One Hundred Thousand Bundles"), held in the Imperial Collection, has been famous since the Muromachi period and testifies to the extraordinary esteem in which these blades were held. A kodachi transmitted in the Nabeshima family of the Ogi Domain in Hizen Province is valued not only for its workmanship but as a rare documentary survival of the short-sword form from this early period. Across the full range of surviving work — from signed ubu tachi to greatly shortened o-suriage mumei katana attributed by tradition — Nobufusa's output is consistently described as possessing koko, the archaic fragrance and classical dignity that define the finest Ko-Bizen production. His blades occupy a pivotal position at the transition from the late Fujiwara aesthetic to the emerging Kamakura idiom, and they remain indispensable material for understanding the origins of the Bizen sword-making tradition.