The published sources open their account of Kanemitsu with one fixed sentence: he is "the mainline heir of the Osafune school, following Kagemitsu"[[c:1]]. Son of Kagemitsu and fourth master of the line that runs from Mitsutada through Nagamitsu and Kagemitsu, he stands as the leading Bizen smith of the Nanbokucho period. His dated works span what the NBTHK calls an unusually long period, roughly forty-five years from Genko 1 (1321) at the close of the Kamakura period through the Joji era (1362-1368), and some designations carry the span to Oan and read it as fully fifty years. So long a working life raises, in the sources' own framing, the question of a first and a second generation, with no settled view as to where the division should fall; the later master is known to the record as "Enbun Kanemitsu"[[c:2]].
His hand divides at a watershed the published sources place in the Jowa and Kan'o eras (1345-1352). Until around Koei both tachi and tanto keep standard proportions, tempered either in a suguha tone mixed with gunome or in the kataochi-gunome he inherited from his father, work that in the recurring judgment of the designations "wholly follows the father Kagemitsu's manner"[[c:3]]. From Jowa and Kan'o the build turns grand, and the sentence nearly every later designation repeats takes over: "a notare-dominant hamon that had not existed before appears, and is met most often around Bunna and Enbun"[[c:4]]. The broad, unhurried notare and the angular kaku-gunome are alike singled out as "what Kanemitsu excelled in"[[c:5]], and one Tokubetsu Juyo description calls the angular gunome "the construction he favored from first to last"[[c:6]]. Against the rounder returns of the earlier mainline, his boshi runs in midare, often thrusting up before a pointed tip.
Even at the grand scale the forging holds. The jigane is itame mixed with mokume, and the NBTHK remarks of one Tokubetsu Juyo katana that it shows not the slightest loosening or coarseness of the surface pattern from base through tip. Fine ji-nie adheres thickly, fine chikei enter, and a midare-utsuri stands out, often called vivid, the steel bright; on the early ubu-signed pieces the reflection is rather a sugu-utsuri or bo-utsuri over a tight ko-itame. The temper is for the most part nioi-dominant with ko-nie. Kinsuji and sunagashi gather toward the koshimoto, small tobiyaki and yubashiri-like effects appear in places, and ashi and yo enter freely. To this he adds a distinctive program of carving: bonji, gomabashi and suken, and above all the cursive grass-style kurikara[[c:7]], a composition the sources note recurs on works of Kanemitsu and Tomomitsu, and at times Chikakage.
Most of what survives from the late phase is the o-suriage mumei katana of the Enbun-Joji build: wide in mihaba with little taper from base to tip, the kissaki large, the sori shallow or moderately deep. Beside it stand the sunnobi hira-zukuri tanto and ko-wakizashi, broad and thin with shallow sori, and the long hira-zukuri blades signed on the sashi-omote, made as uchigatana from the outset, of which the Uesugi "Suijin-giri"[[c:8]] is the recorded example. Signed work is plentiful for so heavily shortened an oeuvre, one hundred ten signed against ninety-eight unsigned among the blades gathered here, the long signatures reading Bizen no Kuni Osafune-ju Kanemitsu[[c:9]] or Bishu Osafune-ju Kanemitsu[[c:10]], many with dates. The strengthened nie of the late manner the sources read with their own hedge, "possibly under the influence of the Soshu tradition"[[c:11]], adding that "since the nie also is emphasized, the work is known in the world as Soden-Bizen"[[c:12]]. The older designations go further only as a question: one Juyo note finds in the turn to notare "the relation to Soshu Masamune, together with the succession of a first and second generation"[[c:13]], the Masamune-pupil tradition held open, never asserted. The many shortened mumei blades carry kinzogan attributions of the Honami line, Kotoku and Koson among them, which the NBTHK in case after case upholds.
Within Bizen his place is fixed by what he carried and what he introduced. The kataochi-gunome descends to him through Kagemitsu alone within the school's mainline, and the notare is his own addition, the broad, unforced midare that, in the words of one Tokubetsu Juyo description, this smith pioneered among Bizen craftsmen. His grand manner passes into late Osafune through his circle: the published sources read related blades as work of the sphere surrounding Kanemitsu, and the cursive kurikara he favored recurs in Tomomitsu.
Fujishiro grades him Sai-jo saku, and two hundred thirty-seven designated works stand on record. No National Treasure is among them, but thirteen blades hold the rank of Important Cultural Property, and the named swords cluster there: the meibutsu O-Kanemitsu (大兼光) and the tachi of Uesugi Kagekatsu's hand-picked thirty-five, both cited in the record as Important Cultural Properties, and the meibutsu Nami-oyogi Kanemitsu (波游兼光), whose gold inlay records the ownership of Hashiba Okayama Chunagon Hideakira, identified as Kobayakawa Hideaki. Forty of his blades hold the Tokubetsu Juyo rank, the most of any swordsmith, and with the Juyo blades the two tiers carry two hundred two. The provenance roll is deep, sixty-nine blades with recorded histories: Ashikaga Takauji, Uesugi Kenshin and Uesugi Kagekatsu, Toyotomi Hideyoshi, Todo Takatora, and the Kuroda, Date, Hosokawa, Maeda and Owari Tokugawa houses; one Juyo katana went to Tokugawa Iemitsu as the bequest of Sugihara Hoki no Kami Shigenaga, and another descended in the Masuda family, hereditary elders of the Choshu domain. The Important Cultural Property and Juyo Bijutsuhin pieces rest as patrimony in shrines, museums and long-held collections, the Tokugawa Art Museum, the Sano Art Museum and Eisei Bunko among recorded holders. For the collector the field is less closed than with most names of this rank: blades of the Tokubetsu Juyo and Juyo tiers, many of recorded private whereabouts, appear from time to time. Yet most are held rather than traded, and a signed and dated piece of either phase is a landmark when it comes.
