Kuniyasu of , whose two-character signature 国泰 is also read Kunitai, is by the published record traditionally held to be the son of the school's founder Tarō Kunimura, who is himself transmitted as a grandson of Kuniyuki of Yamashiro. His extant dated works carry the eras Enkyō, Gentoku, Shōkei and Kenmu, placing him at the close of and into the earliest ; a dated Gentoku 2 (1330) is among the firm anchors of his hand. The group, the published sources explain, settled at Kumafu in Kikuchi District and prospered there from the late period through the , and its work resembles the Yamashiro school so closely that the school is said to show little pronounced individuality from one smith to the next. Within that uniformity Kuniyasu is the smith the sources single out: he is named one of the leading hands of the line, and his individuality, they write, shows in a style that within the school is the most strongly -laden.
That strong is the heart of his hand, and the published commentary returns to it again and again. The school as a whole runs subdued, its somewhat and the activity within the calm; Kuniyasu's blades do the opposite. His temper is a admitting , and shallow , with and entering and gathering thickly; in the upper half the edge frays into and takes on a -like aspect, while fine and run densely through it. Where the rest of the line holds a plainer line, his is the least plain, and the turns bright and clear rather than sinking. The published sources put the matter as a near-formula across his designations: within the group "a slight individuality can be perceived in that his work shows the most strongly -laden appearance." It is this, not any borrowed resemblance, that fixes him within the school.
The forging beneath that temper is an or , generally well packed yet flowing in places toward , so that the grain stands a little; very fine is laid on thickly and delicate enter densely, at times with a mottled - cast. Over this the school's whitish stands in the , the very reflection the published sources name as one of the points that separate from its bright parent. On Kuniyasu the is present but his brighter, more -laden steel tends to crowd it; on his finest , the commentary records, the tightly knit "is well refined with a bright steel color, the bright and thick, recalling at a glance the work of Kunimitsu of the home province." The closes to a , the tip frequently brushed with ; on his broad late it turns back in the school's larger with a shallow , the rounded, shallow-return being itself one of the cited points.
His work is read in two registers. The signed survivals are or lightly shortened , slender and deeply curved, and that by the very end of grow broad and a touch , thick in and nearly ; the is a large two-character signature cut near the tang-tip. One dated is signed in a somewhat thick six-character chisel "Namu-Tenjin Kuniyasu" with a Gentoku 2 date, another adds a Kikuchi-jū residence inscription. The second register is the shortened : blades attributed to Kuniyasu, and others carrying a later inlay attribution. Several keep a ring-shaped wa-zori and a Kyoto air that recall at first glance, but the in the , the and the settle the appraisal as , the level of the work and the strong then narrowing it to Kuniyasu. The published sources caution that the 国泰 name continued: a two-character Kunitai inscribed Kikuchi-jū is judged not the first generation but a -name successor of the mid-to-late , recorded in the , yet keeping the founder's strong edge- and bright and .
What distinguishes him is best drawn from his own blades rather than from the school around him. The judges call one of his "a comparatively uncommon -leaning work for the working range of this school," the forging singled out as distinctly superior, and they note that compared to the school's usual blades the strong adherence of in both and shows his individuality, the steel "of excellent quality and distinctly superior." One earlier appraisal goes further, finding that with his strong his work "corresponds rather to Yamato pieces than to the group," a reading that places his force a step away from the Kyoto manner the school otherwise keeps. The signature itself is a school tell: the right half of the enclosure in the character 国 is cut into an ear-like shape, the published sources note, a manner shared across the line and "not to be confused with other smiths." His is therefore the bright, -strong reading of an otherwise quiet school, and a plain can in turn be mistaken for at a glance.
In Fujishiro's grading Kuniyasu is Jō-jō . The designated record on which his name rests is one Important Cultural Property, two and a substantial run of blades, thirteen in the and tiers together, across both signed and and shortened attributed ; signed survivals, the published sources observe, are comparatively few. His provenance carries some weight of history: a shortened bears a Genna 3 (1617) gold-inlay attribution recording that it was shortened by one Murayama Gensuke and was formerly held by Hori Hidemasa, its blade-school sobriquet "Sokonuke-hishaku," a bottomless ladle, a witticism that "even water will not pool" boasting of the cutting edge. Other recorded holders include the Asō family and a piece with an Imperial connection, and a blade is held today in the Nagoya City Museum. For a collector, an Kuniyasu is not wholly beyond reach: his attributed and the occasional signed stand among the tradeable designated tiers and come to market from time to time, with patience, while the Important Cultural Property and the long-held pieces remain patrimony rather than stock. He is the brightest, most -laden hand the school produced, and the most readily known of an otherwise quiet line.