Masamune of Province was a disciple of Kunimitsu, the founder of the - tradition. Together with his fellow pupils Yukimitsu and Norishige, Masamune inherited and built upon his master's manner, further emphasizing , , and to guide the tradition toward its completion. Among these three outstanding talents, the consistently places Masamune "at the very summit," noting that his and are "the most refined and sophisticated." His principal period of activity is understood to be the late period, with a lower limit extending into the early period; the old transmitted theory that he died in Koei 2 (1343) "cannot be dismissed out of hand." His works encompass both and forms, with typically showing standard or somewhat broad and of varying extension, and characteristically in the eight- range with shallow .
Masamune's characteristic style is built upon a -based in which the temper "becomes intensely covered with and breaks down." The gathers, thickens, and congeals; "leap and move incessantly"; spills into the to form ; and conspicuous are "woven throughout" the ground. The describes this as "an extraordinarily varied mode of workmanship that may be called Masamune's own originality, giving the impression of viewing sansui (splashed-ink landscape painting)." His is typically mixed with , forged tightly, with fine adhering thickly and entering frequently; the steel is characteristically described as "clear and bright." His is consistently praised as "bright and clear" (akaruku ). The also recognizes a second, calmer mode of workmanship — pieces showing a -like -based temper with finely wrought and delicate — demonstrating the breadth of his stylistic range. In both modes, Masamune "skillfully handled several kinds of steel of differing carbon content" and "brought the aesthetic subtleties of to their highest level."
The 's evaluative language for Masamune is singular in its consistency and elevation. His work is described as representing "the very limit of expression" and "the ultimate extreme of ," a "creative domain" that he alone opened. The recurring characterization of his tempering as evoking landscape painting — an analogy invoked across nearly every — frames his achievement not merely as technical mastery but as an aesthetic breakthrough of the highest order. His contribution is assessed in civilizational terms: he "made a major contribution to elevating the artistic quality of the Japanese sword." Individual blades are praised as displaying "the very highest level of technique even among superior - works," with and that are (sound and well-preserved) and that "fully manifest the subtle fascination unique to this smith." His works carry illustrious provenance through houses and the Tokugawa shogunate, many recorded in the Kyoho -cho and authenticated by successive generations of the house — a legacy that the regards as "fully confirming the high esteem in which Masamune has been held since old times."