Masamori (畠田真守) is traditionally transmitted as either a son or a disciple of Moriie (守家) of the line in Province. Extant works bearing dates from the Kenji, Koan, and Shoo eras establish his period of activity firmly in the late period. While the majority of his signed works bear a two-character , examples with longer inscriptions reading " no -ju Umanojo Masamori " are also recorded. Sword reference compilations () note that there appear to have been at least two generations working under this name; Honma observed that works bearing a large signature (omei) seem to belong to the first generation, while those with a small signature () appear to be by the second. Swordsmiths using the name "Masamori" are also known in Ohara of Hoki Province during the period and in the school of Province during the period; their signature styles and workmanship differ from one another.
In workmanship, Masamori follows his father Moriie, forging with pronounced (frog-roe) elements and considerable variation. Compared with Moriie, however, his tends overall to present somewhat smaller-patterned designs. His characteristically shows in which appears distinctly, a hallmark of classical craftsmanship. Among the large-signature works attributed to the first generation, conspicuous - and closely resembling Moriie are especially notable. Yet Masamori is also capable of marked restraint: his signed displays a finely detailed surface of well-packed with a narrow in , demonstrating versatility across both flamboyant and austere tempering modes. Where the is rendered in , it is enlivened by varied forms with abundant and , yielding an animated yet controlled temper pattern. In general, signed works include both and , and it is typical, as the observes, that "the tempering is not excessively high" -- though some flamboyant exceptions with pronounced do exist.
Signed works by Masamori are encountered from time to time, yet the consistently notes that his output, while clearly identifiable within the lineage, is "regarded as somewhat inferior" to that of Moriie. A preserved in the Seikado Foundation collection (formerly Iwasaki Koyata) retains with a bold, imposing form and distinctly standing , while another in the Kurokawa collection maintains an archetypal early silhouette with pronounced -zori and retention of , its displaying - and with abundant and . A rare signed is singled out as possessing "high documentary value" and as "an outstanding piece of archaic elegance, brimming with dignity." As both signed and appraised works -- including a shiro- attributed to Sanada Masamori -- these blades collectively constitute precious material for understanding the full range of craftsmanship in the generations following Moriie.