Kuninaga worked at Gojō in Kyōto at the close of the period and into the early , and the published sources count him among the first rank of the old Kyōto makers: "Kuninaga is one of the representative smiths of the ko-". He is transmitted as a son or grandson of Munechika, and in one entry as Munechika's disciple. Because he and Kanenaga, given variously as his elder brother or his father, both lived in the Gojō quarter, he is known as Gojō Kuninaga. The most famous blade to carry his name is the Tsurumaru Kuninaga, listed as in Honma's inventory of the Imperial collection, whose entry judges it outstanding among the works of the name, "a masterpiece among masterpieces". The published sources note that his signatures are not uniform, and that a whose differs from the Tsurumaru and from the Jingū can still be acknowledged as the same hand. Signed work is exceedingly scarce, only a few and a single , and of them all the sources write that they "display an archaic elegance and a richly resonant character".
His signed keep a slender, graceful -buri form, the curvature high at the waist and easing toward a , the old shape preserved even where the blade has been shortened. The temper is a soft, bright , drawing in and with and . Its is soft and the well adhered, with fine and . Along the crests of the temper run and small , variations the commentary calls frequent among the old Kyōto makers. On one signed the turns in with , well swept with , the tip pointed and the return a little longer. The sources find strength in it that does not look rough, and see there "the skill of a master craftsman".
The is a well-packed , standing a little in places and mixed with and . Fine settles evenly, delicate enter, and in places a faint stands. An of the fifty-sixth session shows the same refined forging under a classical shape, and the published sources find the highlights of old Kyōto work conspicuous on it and the whole "unmistakably graceful". Among the Gojō school they liken that above all to Kuninaga. The signed , an Important Cultural Property, is a double- blade forged in mixed with , its temper a -toned line with , recorded as work.
The attributed blades form the other reading of his record. On an the sources read a "strong Yamato character, yet with the lingering manner of Munechika present", and place it a little later in date. Another , of standard width with a thick and heavy in hand, has a flowing, standing under thick , with in parts. Its base mixes , , and angular , with , and -like . Of that blade the sources write that it "clearly demonstrates the distinctive traits of Gojō Kuninaga in both and ". A , short and dignified, carries a -toned temper with , and and a . The judges call it "exceptionally sound for a piece of this period" and fully accept the Gojō Kuninaga attribution.
What sets his work apart is its scale and poise. His stays small and antique, and even on his strongest the sources find that "a well-ordered typical of Kyōto work predominates". With Kanenaga he stands at the head of the Gojō line, and his attributed blades are read through the lingering manner of Munechika.
He has no National Treasures. Ten designated works stand on record, among them one Important Cultural Property, the signed , five blades, the prewar and the Tsurumaru in Honma's inventory. The commentary on one signed calls it extremely valuable for understanding the style of a smith whose signed works are rare. Provenance in his corpus reaches the Date house: one signed was owned by Date Muneaki when it was recognised in 1937, and another carries a Kōchū of Genroku 10. With only five blades in the tier and his signed an Important Cultural Property, a signed Gojō Kuninaga comes to light only seldom, and a privately held example is among the most notable things an early Kyōto collector could encounter.