Kuniyasu was born in Yamashiro Province and is traditionally held to have been a grandson of Kunisue. He later relocated to Province, where he is regarded as the founder of the Chiyotsuru lineage. Sword reference works place him around the Joji era (1362-1368), situating his active career in the period. His work preserves the core characteristics of the school while bearing the marks of a provincial sensibility that distinguishes his hand from the mainline Yamashiro tradition.
Kuniyasu's blades display mixed with and, in places, , with a pronounced tendency toward -- a standing grain that, together with thickly adhering and plentiful , imparts a slightly whitish or at times blackish cast to the steel. This prominent grain texture, producing a tone somewhat removed from the refined clarity of Yamashiro's homeland, is central to his identification and conveys what the describe as a "northern provinces" feeling. The is characteristically a with a slight admixture of , containing and well-adhering ; slight along the edge and a -like nuance are frequently observed. Thick adheres throughout, with fine and running through, and the is bright. In the , vigorous sometimes produces a flame-like -style impression, while coarser, especially brilliant may appear, displaying a rusticity beyond what is typical of mainstream work.
Kuniyasu's surviving blades, though invariably and unsigned, present powerful forms with broad , minimal taper, and extended configurations characteristic of the period. Both and are frequently praised as exceedingly -- sound and well-preserved. His work occupies a significant position as the bridge between the refined tradition of the capital and the vigorous provincial smithing of .