The Masatsune lineage represents one of the two principal pillars of the school, active in Province from the close of the period through the early period. Together with Tomonari, the Masatsune name-line forms what repeatedly characterize as the "twin peaks" (soheki) of . It is understood that three or perhaps four smiths worked under this name across successive generations, and slight differences in their manner of signing have been noted. Among smiths, the Masatsune line has left the greatest number of extant works, "with no inconsistency in quality." Smiths of the name also existed within the group in neighboring Province, and their workmanship is acknowledged to be close in character.
The collective style attributed to Masatsune is distinguished, first and foremost, by the excellence of the forging. assessments consistently observe that while Masatsune "yields somewhat in the excellence of " to Tomonari, "in the refined quality of the forging there are works that surpass" him. The is typically a tightly knit mixed with , bearing abundant and fine . A defining trait is the clarity of the : where Tomonari's tends to remain inconspicuous, Masatsune's "rises with vivid clarity" and is frequently described as "standing out distinctly." The is characteristically -based with , mixed with and occasionally small , producing what the terms a "somewhat more technical, devised character" compared with Tomonari's more archaic temperament. Rich interior activities of and enter well, and and appear with regularity. The runs and turns back in , a pattern so consistent it serves as a distinguishing diagnostic. The is frequently described as "bright" (), and the overall is thickly and finely attached.
This body of work occupies a distinctive position within the tradition as the lineage that most fully realized the potential of craftsmanship in the early period of Japanese swordmaking. language repeatedly returns to phrases such as "the excellence of the forging is fully apparent," "consummate forging with not the slightest looseness," and "bright steel color and excellent-quality forging." Where Tomonari is celebrated for the graceful, feminine () beauty of overall form, Masatsune is valued for a more polished, technically refined character that the regards as representing another, equally valid aesthetic within the school. The school's works span a range from blades retaining deep -period archaic flavor to those showing the more florid and vigorous characteristic of the -period generations. Related contemporaries including Kanehira, Toshitsune, Sanetsune, and Yoshikane share overlapping traits, yet the Masatsune line remains identifiable through its superior forging, vivid , and technically sophisticated tempering.