Osafune Moromitsu is recorded in sword reference works as the son of Tomomitsu (also rendered Rinkō) and the father of Morimitsu, placing him squarely within the main Osafune lineage during its late Nanbokucho florescence. Dated works survive from the Eiwa era (1375) through Oei (1394-1428), establishing an active career spanning roughly three decades at the transition between the Nanbokucho and early Muromachi periods. He stands as one of the representative smiths of the group collectively referred to as the ko-zori-mono -- makers of blades with comparatively slight curvature -- a stylistic cohort that defined a distinct chapter in Bizen production. Reference works further list several generations bearing the same name extending into the Muromachi period, and the question of whether Oei-dated works belong to a second generation remains a subject of ongoing scholarly inquiry.

Moromitsu's technical character is distinguished by a consistently rendered small-pattern aesthetic. His kitae typically presents itame-hada mixed with mokume, often with a finely standing grain, thick ji-nie, frequent chikei, and faintly appearing utsuri or conspicuous midare-utsuri. Upon this forging ground he sets a hamon of ko-choji mixed with ko-gunome, ko-notare, and pointed elements, with saka-ashi tendencies appearing here and there and ko-ashi entering well. The temper is characteristically nioi-dominant with ko-nie, and fine sunagashi run through. The intermixture of multiple ha forms, the occasional saka-ashi tendency, and the overall rendering into small-patterned expression well demonstrate the hallmarks of ko-zori works. In comparison with such contemporaries as Morimitsu and Yasumitsu, his manner is more subdued, and a number of his tachi retain the classic silhouette of koshizori with pronounced funbari and ko-kissaki or compact chu-kissaki. His jigane can be strongly saeru, showing a blue-black tonal cast, and his forging is characteristically bright and clear.

Within Moromitsu's oeuvre, the finest examples display a varied range of hataraki while maintaining a high degree of completeness, with full and rounded nioiguchi and ji and ha that are kenzen in every respect. Several blades carry rare date inscriptions -- Eitoku 1 (1381) and Shitoku 1 (1384) among them -- that are precious as documentary material. His production also includes uncommon forms such as ken, of which examples are notably scarce in any period. As an ubu tachi preserved with original nakago, his signed works constitute valuable source material for research into the Bizen smiths of the late Nanbokucho and early Muromachi eras, and the features of his signature share points in common with other Bizen works of the Oei era, further enriching the documentary record of the Osafune tradition.