Kunitoshi is traditionally regarded as a son of Kuniyuki of Yamashiro Province. Among extant works attributed to this smith, there are those that do not prefix the character "" in the signature -- the so-called "two-character Kunitoshi" (Niji Kunitoshi) -- and those bearing the three-character inscription " Kunitoshi." Judging from surviving dated examples, the working span extends from Koan 1 (1278) through Genkyo 1 (1321), a period of roughly forty years; even as the career of a single individual, this presents no chronological difficulty. Indeed, a signed Kunitoshi dated Showa 4 (1315) bears an inscription recording the maker's age as seventy-five, which, reckoned backward, places the sole dated Niji Kunitoshi work at age thirty-eight -- an entirely plausible figure. Nevertheless, because differences in workmanship between the two groups can be observed to a considerable degree, both the view that they are the individual and the view that they represent different smiths have been advanced, and the matter has not yet been definitively settled. The Kaifunki preserves a noteworthy passage stating that Niji Kunitoshi was Kuniyuki's heir and died young, while Kunitoshi was Kuniyuki's second son, from whom the use of the "" character began.
In terms of workmanship, Niji Kunitoshi tends toward a powerful with wide , deep , and a compact of style. The is typically a tightly forged with fine adhering thickly and delicate entering well; stands out prominently, and the steel is bright and clear. The favors a flamboyant mixed with that recalls the school, yet is distinguished from work by its firmly -based construction. Plentiful and enter within the temper, the is bright, and and appear. A particularly characteristic feature is the so-called Kyo -- the tendency for within the , especially on the , to slant diagonally toward the in the reverse direction from convention. The is typically straight, turning back in . By contrast, works bearing the Kunitoshi signature more often show a slender, elegant bearing together with refined -based tempering in , though these too are marked by thick , fine , and prominent .
Taken as a whole, the oeuvre attributed to Kunitoshi encompasses a remarkably broad working range -- from the grand and decorative manner associated with Niji Kunitoshi to the restrained, courtly elegance of Kunitoshi -- and within both modes the quality of execution stands at the highest level. Whether the product of one individual or two, these works occupy a pivotal position in the lineage, bridging the robust forging tradition inherited from Kuniyuki with the refined aesthetic that would define subsequent generations of Yamashiro smithing. Both and are characteristically bright and clear, and the finest examples display a depth of activity and a subtlety of internal variation that place them among the most accomplished achievements of the mid-to-late period.