Kiyotsuna is the de facto founder of the Nido school of Suo Province. Though tradition holds that the lineage began around the Hoden era (1135–1141) with Kiyozane or Kiyohira, no securely attributable works by these figures survive, and Kiyotsuna is today regarded as the school's progenitor. The earliest dated work is a at Itsukushima Shrine inscribed "Bun'ei 2, third month, Kiyotsuna" (1265), placing his active period in the mid-to-late era. Regarding the origin of the name "Nido," the most persuasive theory holds that it derives from the school's residence in Niho-sho within the province. Suo Province contained many estates belonging to major temples such as Todai-, and the strong Yamato coloring in the Nido school's manner is thought to reflect exchange with the Yamato heartland. Thereafter, smiths bearing the signature continued without interruption into the period and even into the era.
Kiyotsuna's forging characteristically shows that flows overall, with places tending toward and taking on a standing-grain tendency; fine adheres closely, with delicate , and conspicuous appears — a hallmark recognized as a distinctive trait of the group. The is typically a narrow or mixed with , displaying an overall tendency — that moist, soft quality the identifies as characteristic of both this smith and the Nido school. Works show , , and , with a that is bright and clear. The bosshi turns back straight in . His retain a slender form with high , somewhat thick , and a high — constructions frequently encountered in this school — allowing one to apprehend the graceful silhouette of the late period.
Surviving works by Kiyotsuna are now rare, and the consistently describes them as "exceedingly valuable" and "extremely precious" as reference material. Signed examples with preserving original taka-no- file marks and the characteristic old-style inscription are singled out for particular commendation. Blades judged to be first-generation work demonstrate ample , show "not the slightest looseness in either or ," and are assessed as — sound and well-preserved — exhibiting "an outstanding level of workmanship." His oeuvre firmly establishes the Nido school's identity: a Yamato-inflected tradition distinguished by in the steel and in the temper, representing a provincial lineage of quiet refinement and scholarly significance.