The Kunikane was born Hongō Genzō in Bunroku 1 (1592) at Kokubun-Wakabayashi in Sendai, Mutsu, and entered the service of Date Masamune as a retained smith. By his lord's command he went up to Kyoto and studied under no Kami Masatoshi; in 'ei 3 (1626) he received the court title Yamashiro Daijō, and he styled himself a descendant of the later line of Yamato Hōshō Gorō. That self-styling is the key to him. In the opening decades of the period, when the manner in and was the fashion of the day, Kunikane set himself against the current and gave his whole working life to reviving the -forging, -tempering Hōshō- of old Yamato. The published sources describe a hand that never wavered from that purpose, and the modern designation record bears it out: of the blades on record every signed example is in his own name, with not a single unsigned attribution among them.
His characteristic hand is constant to the point of being unmistakable. The forging is a tightly packed , at times running into , carrying fine thickly applied and frequent , the steel notably clear. A often rises from below the , and the published sources name this rising water-shadow a personal habit of the smith, calling it on one a feature that 「初代国包の手くせといえる」, the kind of small confirming detail that settles an attribution. Over that he tempers a or , frequently broad, shallow in , the deep and bright. The activity is the Yamato kind rather than the : along the runs general , with and set freely into the line, , and uchi-noke mixed in, and entering.
The is where he is read first and where he is most himself. Fine and the abundant over a clear, well-packed recur on nearly every blade, the forging only growing more refined as it tightens. The is the Yamato finish, running straight into a -like point with vigorous ; the published sources find an archaic fragrance in it even where the rest of a blade is plain. On this last point they are candid in a way that is unusual for designation commentary: measuring him against the early Hōshō, they name where he falls short, citing 「物打上の変化に乏しいことと、帽子が平凡な点にある」, a relative want of variation in the and a commonplace . The entry holds that the quality of both and on his representative dated is nonetheless excellent.
One consistent hand divides into two registers by the shape it takes. The standard work is the , and long-signed, very often dated, with a high , shallow and an elongated , over which the broad bright sits on the tight ; his dated and from 'ei 4 and 'ei 9 are the touchstones for studying his oeuvre. The rarer register is the , of which the published sources note that very few survive, prizing them as reference pieces. On these the temper opens out: the upper half takes a somewhat broader , the thickens and coarsens in places, resembling appear, the tends toward , and the carvings, a plain and a with , are cut with deep channels that reproduce a feature of old Yamato work. Of the Onikiri the commentary says it is a piece in which 「初代国包の本領が遺憾なく発揮された」, the smith's true strengths brought forth without reserve.
What sets Kunikane apart in his own period is exactly this fidelity to an older province. The published sources record that 「作風は一貫して大和保昌伝に終始し」, his manner kept to the Yamato Hōshō tradition from first to last, forging and tempering with uchi-noke, and , the well adhered and the tending to . His bright and Yamato finish set him against the -fashion smiths around him, and his disciplined over a clear distinguishes him from the Hōshō he revered, whose and he could not quite equal. He retired in Shōhō 2 (1645) and handed the headship to his eldest son Kichiemon, the second-generation Yamashiro no Kami Kunikane, founding a Sendai Kunikane line that carried the Hōshō- to the end of the period; the remains the standard against which the later generations are judged.
For the collector he is a name of real standing. The published record runs through one Important Cultural Property, two prewar Jūyō Bijutsuhin and twenty-nine blades in the and tiers, thirty-three designated works on record in all, every one of them signed. There are no National Treasures. His finest, an , signed and dated preserved in its original form and held in the Uwajima Date family, the published sources call equal to or surpassing the old Hōshō, 「古保昌に優るとも劣らぬ作域」, and a masterpiece of imposing presence. His provenance is grounded in the houses he served and a few long-private hands: the Date and the Uwajima Date families above all, with recorded blades reaching the Imperial collection and the keeping of named collectors such as Kimura Sadazō. A signed Kunikane is not beyond a serious collector's reach in the way a great master is, yet the blades are mostly held rather than traded, the rarest of all, and a dated example in good state comes to market only from time to time. When one does, it is a clear and self-contained document of how, in an age that had turned to , one Sendai smith chose instead to forge his way back to old Yamato.