In Iwami Province, called Sekishū, a line of smiths signing Naotsuna (直綱) worked in the manner of the - far from , carrying that tradition into the San'in region during the period. The record several smiths of this name, the older tradition books placing a first generation in the Kenmu era, a second in Eiwa, and a third in Ōei, though the is careful to note that a strict separation of the generations still awaits further study. The first-generation Naotsuna, sometimes given the family name Ishikawa, is transmitted as a pupil of Masamune and counted among the so-called Masamune Juttetsu, the Ten Disciples; the appraisals repeatedly add that, considered chronologically, a direct connection to Masamune seems difficult, and that the correctness of the tradition must be left to future research. Signed work of the first generation is rare, and the signed Iwami no Naotsuna is described as exceedingly valuable for that reason.
The shared hand is built on a forging of mixed with that tends to stand () and often runs with , thickly covered in with entering well; the steel reads dark, an iron-toned kanashoku with a blackish cast that the appraisals treat as a recognition point. Upon this ground the temper is a -based , the frequently angular and run together in linked sequences, mixed with , , and pointed . and enter densely, adheres thickly and at times coarsely, and and run prominently through the , often joined by , , and intermittent . The is typically with vigorous , returning in or . These traits the reads as the influence of the - made plain, sharing an underlying current with and ; one fourth-session draws the comparison directly. A -flavored, -leaning element is occasionally mixed into the , and faint is noted on a single , but the -laden character governs. To recognize Naotsuna's hand is to read this combination together: dark standing , an angular base, and abundant and , set in the wide and of the Enbun and Jōji moment.
The line extends through smiths the name in their own right. Sadatsuna, recorded as a son of the first-generation Naotsuna and likewise resident at Izuha (Deawa) in Iwami, works in a manner that closely resembles Naotsuna's, seen both in a -based and a -based style and marked in either case by well-applied and vigorous ; his signed , including a six-character Sekishū Deawa Sadatsuna, anchor the attribution of his pieces. Masatsuna, given as a son of Sekishū Naotsuna and active from into the period, is met in a bold, open of texture with standing grain. The Suesada lineage, begun by a son of Sadatsuna, carried the tradition further into the period and produced an exceeding five , and the appraisals trace still later Nagahama followers such as Shōsue, Shōsada, Yōtei, and Rinshō. As points the register fixes the dark kanashoku, the angular and locally linked , the thick and sometimes uneven , and the conspicuous and , with the su- and carvings recorded on several blades. Across the surviving body of signed and work, gathered in the Jūyō-Bijutsuhin registers and in references such as the Kokon Kaji Bikō, Naotsuna stands as the carrier of the manner into Iwami, a provincial reading of Masamune's tradition recognized by its own settled vocabulary.