Tomomitsu (倫光) was a swordsmith of the Bizen Osafune school active during the Nanbokucho period, counted among the foremost disciples of Kanemitsu; one tradition further transmits that he was Kanemitsu's younger brother. Dated works that survive range from the Jowa era (1345) through the Eiwa era (1375–1379), placing his productive career squarely within the Enbun-Joji florescence of mid-fourteenth-century Bizen. The NBTHK consistently describes him as the smith "whose style stands closest to that of Kanemitsu" within the Osafune circle, and in level of accomplishment "his work at times approaches that of his master." His name appears under several readings in the literature — Tomomitsu, Rinko, Rinmitsu, and Henko — all representing the same characters (倫光), a reflection of the multiple Sino-Japanese pronunciations available for the mei.

Tomomitsu's forging is characteristically a fine itame mixed with mokume, often described as tightly worked and well-kneaded, producing what the NBTHK calls an exceptionally seiryo (excellent-quality) texture. Thick ji-nie adheres across the surface, fine chikei enter well, and utsuri — whether midare-utsuri, sugu-utsuri, or an extremely faint standing variety — is a recurring presence. The hamon is built on a notare foundation, into which gunome, ko-gunome, choji, ko-choji, and togariba are mixed in varying measure; it is predominantly nioi-deki with ko-nie, and the nioiguchi tends toward a tightened appearance (shimarigokoro). Fine kinsuji and sunagashi appear in places, and scattered tobiyaki and yubashiri add further interest. The boshi frequently enters in midare-komi, turning back pointed or in ko-maru, at times showing hakikake. Many blades bear elaborate horimono — true-form kurikara, bonji, gomabashi, suken — a feature "often encountered in the main line of Osafune work of the Nanbokucho period, especially in Kanemitsu and Tomomitsu." His sugata overwhelmingly reflects the grand Nanbokucho-period taihai: wide mihaba with little taper between base and tip, and an extended chu-kissaki or o-kissaki.

The NBTHK's evaluative language for Tomomitsu is remarkably consistent across decades of designation sessions. While resembling Kanemitsu, his works "also reveal Tomomitsu's own characteristics, particularly in the relaxed notare-based temper"; the slightly pointed crests of the notare and a tendency toward standing grain in the jitetsu are repeatedly cited as distinguishing features that "make the attribution readily acceptable." Blades are praised for a "composed and unhurried" (yuyo) tempering pattern that avoids monotony, for the refined quality of forging that demonstrates "the high technical level of the orthodox Osafune line," and for kenzen (sound and well-preserved) condition in both ji and ha. Signed, dated examples are singled out as possessing "exceptionally high documentary value." Taken together, the designation records position Tomomitsu as a first-rank successor within the Kanemitsu lineage — a smith whose expansive, generous midare and refined Bizen forging place him at the very threshold of his master's achievement.