Kuninaga was a student of Kunitoshi who later moved to Nakajima in Settsu Province, from which tradition he is referred to by the appellation "Nakajima ." Sword reference works list two generations bearing this name, recording the first as active around the Gentoku era (1329-1331) and the second around the Shohei and eras (1346-1370). Extant signed works are very few. His manner preserves the -school tradition; stylistically it resembles Kunimitsu, though in terms of refinement and dignity "it yields slightly" -- a phrase the repeats with remarkable consistency across every appraisal.
Kuninaga's forging is typically mixed with and , with a tendency toward (standing grain) and thickly adhering ; appear frequently, and a faint often stands up. His is characteristically -based -- whether described as or -- mixed with and , with abundant and and well-adhering . A distinctive feature noted across multiple appraisals is the appearance of Kyo-, the diagonally inclined feet associated with the Yamashiro tradition. Activities along the are rich: , , , uchi-noke, , and appear with some frequency, while the is consistently described as bright. The tends toward with vigorous , and in some examples ends in . His construction favors wide with deep, ring-like curvature and enlarged -- the commanding of the Enbun-Joji period of the .
The repeatedly emphasizes that Kuninaga's works "clearly manifest the characteristics of the school" and are distinguished by their "numerous internal activities and rich variation." His finest pieces are praised as possessing a "severe and spirited" character that "clearly demonstrates technique approaching that of Kunimitsu." With few signed works surviving, each example also carries exceptional documentary value. The school's evaluation of Kuninaga positions him as an important transmitter of the lineage whose bold, -period constructions and vigorous within the temper give his work a martial power that complements, rather than merely echoes, his master's refined elegance.