Naotsuna (直綱) of Iwami Province -- known as Sekishu Naotsuna -- is traditionally counted among the Masamune Juttetsu, the Ten Great Disciples of Masamune. The NBTHK consistently notes that "there were several smiths bearing this name," with old transmission records placing a first generation in the Kenmu era, a second in Eiwa, and a third in Oei, though "the strict separation of these generations still contains points requiring further study." Regarding the claim of direct discipleship under Masamune, the setsumei maintain a measured scholarly reserve: "when viewed in terms of chronology, a direct connection seems somewhat difficult," yet "the definitive correctness or incorrectness of that tradition should be left to future research." What the evidence does confirm is that Naotsuna's workmanship "shares an underlying current with Shizu and Samonji within the Soshu tradition."

The jihada characteristically shows itame mixed with mokume, with a pronounced tendency toward hada-dachi; thick ji-nie adheres, bold chikei enter well, and "the steel color tends toward a darkish, iron-toned coloration." The hamon is consistently built around gunome -- running together in linked, continuous sequences -- mixed with angular elements, ko-notare, togariba, and choji. Thick nie adheres, sometimes becoming uneven with patches of ara-nie; kinsuji and sunagashi appear with great frequency; and yubashiri, tobiyaki, and muneyaki further enrich the edge. The boshi displays vigorous hakikake, in the finest examples becoming kaen-like -- a flame-like manner -- or even ichimai-like. One setsumei observes that with yubashiri and tobiyaki intermingled, the temper achieves "an overall hitatsura-like impression." The nioiguchi frequently shows a shizumi tendency, described as subdued, which together with the dark steel tone gives Naotsuna's work an archaic gravity distinct from the bright clarity of other Soshu-lineage smiths.

The setsumei repeatedly praise Naotsuna's blades as "brimming with a bold and forceful spirit," singling out the powerful Nanbokucho-era forms -- wide mihaba, thick kasane, deep sori, and imposing o-kissaki -- as conveying "an overwhelming impression." The "distinctive gunome-connected hamon" with "conspicuously angular elements" is identified as the smith's most recognizable hallmark, and the richly nie-laden forging with interwoven chikei is deemed "outstanding." Works of particular documentary value include a signed tachi bearing an archaic meiburi and a blade accompanied by an Enpo 7 origami by Hon'ami Kojo. Among blades attributed to this tradition, those displaying the fullest expression of these features are consistently elevated as showing "especially distinguished workmanship."