Kuninaga is the smith the published sources call Nakajima , a pupil of Kunitoshi who left Kyoto for Nakajima in Settsu and carried the manner into the period. The lists two generations of the name, the first about Gentoku at the close of and the second about Shohei and ; only the three-character signature Kuninaga is known, and almost no dated work survives. This entry holds the first generation together with the Nakajima attribution, and the judges are candid about how thin the line between the two generations is: of one signed they write that its generation 「その代別についてはなお検討の余地がある」 (remains open to further examination).
The constant of his work is the . Over a well-forged he mixes and a flowing , the grain tending to stand a little, with thick , frequent and a quiet rather than the bright reflection of the Kyoto mainstream. Upon it he sets a broad or medium into which and enter, with and , well adhered, and and running through. The goes straight to a small , or sweeps with . Most of the carry a plain cut through in kaki-nagashi. On the best of them the judges single out the steel itself, 「温潤でねばり気の感ぜられる地がねは見事である」 (the , warm and with a felt tenacity, is splendid).
The judges fix his in one recurring sentence. His work 「様式的には来国光に似るが、格調の面で聊か譲るところがある」 (resembles Kunimitsu in style but yields a little in dignity), so a blade that reads as yet falls just short of Kunimitsu is given to Kuninaga. They also say plainly that this is a convention to be questioned. Of one the commentary sets out the problem: 「やや技術が劣る直刃出来の作をそれに当てている事が、果して妥当なりや否やという問題に始まる」 (it begins with the question of whether it is right to assign him works of somewhat lesser technique), and for the present it follows tradition. When the evidence is strong they commit, as with a of Kenmu-period vigour for which 「来派の中でも国長に鑑するのが最も妥当と言える」 (within the school, an attribution to Kuninaga is the most appropriate).
Signed work is rare, and the first generation's rarer still: 「殊に初代と鑑せられるものは稀れである」 (pieces judged first generation are especially rare). The judges separate the generations by the chisel. On a signed of slightly wide body they note that, unlike the second generation's thicker and rounder strokes, the first-generation signature is 「二代のやや太鏨で丸味あるものとは異って、やや細鏨で角張るこころがある」 (cut in a somewhat fine chisel with an angular feeling), and conclude 「初代銘である」 (it is a first-generation signature). A preserved with an and a small are judged first generation by signature and manner. A first-generation , they record, is slightly wide with a little , mixed with , a -toned temper with and a tight , the straight to a small round.
A small signed group sits uneasily in this frame and is kept here with that question attached. One is wide and extended with a thin , its mixed with over a standing , and the commentary observes that it is 「一見、初代信国に近似した出来口を示している」 (at first glance close to the first-generation ). Another departs from the tradition with a temper based on . A signed breaks its wide into and , praised as 「来国光に迫る技術が明示された優品」 (a fine piece showing a technique approaching Kunimitsu). The published sources describe the second generation's short blades in just these terms, yet for these pieces they stop short of naming a generation.
For the collector Kuninaga is a scarce name whose signed work is especially few. He has no National Treasures. Two are Important Cultural Properties, one held at Sakurayama Shrine. His standing otherwise rests on 55 blades in the and tiers, one of them a , nearly all of them attributions. The provenance is distinguished. A small judged first generation was, its scabbard records, 「十代将軍家治の指料であったことがわかる」 (the sidearm of the tenth shogun Ieharu), presented by the Owari house. A appraised by Koyu was 「雲州松江藩主松平治郷(不昧)の遺愛の一口」 (a treasured blade of Matsudaira Harusato, Fumai, lord of Matsue). A is recorded as 「西条松平家伝来」 (handed down in the Saijo Matsudaira house). The attributed come to market from time to time and reward a patient collector; a signed first-generation piece is a genuinely rare encounter.