Tomokuni (来倫国), also read as Rinkuni, is transmitted as a son of Kunitoshi and the younger brother of Kunizane within the school of Yamashiro Province. According to certain traditions, Kunizane himself was either a disciple or a son of Kunitoshi, and may also have been the elder brother of Tomokuni. The familial relationships within this branch of the lineage remain a matter of ongoing scholarly discussion. Signed works by Tomokuni are extremely rare: no signed are known, and only a very small number of survive bearing his name. The works most frequently encountered are judged to date to the period and are considered to represent a second generation, the first generation being a direct student of Kunitoshi.
Blades attributed to Tomokuni characteristically display the -period : a wide , thin , slightly extended proportions (), and shallow . The forging is , at times mixed with a tendency and flowing grain, with adhering thickly and entering well; faint may appear. The is typically mixed with , with deep and well applied; , , , and are seen, and strong may run prominently. The tends toward or , turning back in , at times with . Certain unsigned works appraised to this lineage incorporate a -like flavor in the temper pattern, showing workmanship with an affinity to the Hasebe school — a departure from the more restrained manner associated with the main line. From such considerations, the existence of a distinct second generation with a somewhat broader stylistic range has been proposed.
Tomokuni occupies an important position within the later school as a smith whose work bridges the refined Yamashiro tradition of Kunitoshi with the bolder, more vigorous expression of the era. The presence of appraisals dating as early as Genna 7 (1621) attests to the longstanding regard in which these blades have been held. Both and in the finest attributed works display the characteristic traits of the lineage with clarity and soundness, and the scholarly challenge of distinguishing successive generations continues to make Tomokuni a subject of considerable interest in the study of Yamashiro- swordsmithing.