Masatsune (正恒) is a representative smith of the Senoo group (Senoo kaji) within the tradition of Province, a lineage tracing its origin to Noritaka and standing apart from the main line of smiths who characteristically employed the character "Tsugu" (次) in their signatures. According to the , the first-generation Masatsune is placed in the 'ei era of the early period, yet among extant works there are examples that do not descend later than the end of the period, indicating that the name was not confined to a single individual but was borne by several smiths across multiple generations. In neighboring Province, the group also produced smiths of the name at virtually the time, and in workmanship the two lineages are broadly similar — a circumstance that has historically made attribution between them quite difficult. The pattern provides one reliable method of distinction: those with are , while those with are .
The forging of Masatsune's works displays the hallmark characteristics of craftsmanship. The is typically worked in mixed with , producing areas where the grain stands in a fine, mottled manner often described as — the distinctive "crepe-like" texture regarded as a defining trait of the school. adheres well, with interwoven and irregularly appearing that gives rise to a conspicuous -like . The is fundamentally , mixed with , , and ; and enter well, and the tends toward tightness (), with adhering and fine and appearing throughout. The characteristically runs straight and turns back in , at times displaying — a feature noted as particularly indicative of Masatsune's hand. Signatures appear in a two-character inscription, observed in both the and positions, consistently accompanied by the school's prominent file marks on the tang.
Masatsune stands foremost as the representative figure of the Senoo smiths, and his surviving works are not particularly few. Compared to his contemporaries, his workmanship tends to be more subdued, possessing a feeling of restrained, astringent taste (shibusa) and an archaic, deeply flavored character that clearly reveals the characteristic appeal of work. The has repeatedly noted the desirability of condition — blades sound and well-preserved in both and — across his designated pieces, and examples retaining their original with signature intact are regarded as especially valuable. His oeuvre encompasses works ranging from the very end of the period through the late , and taken as a whole, it constitutes an essential body of evidence for understanding the early swordsmithing traditions of Province.