Muramasa was a representative swordsmith of Ise Province in the late Muromachi period, residing at Kuwana in that province. He belonged to the Sengo group, and among extant works the earliest dated example bears the date Bunki 1 (1501), inscribed with the full signature "Seshu Kuwana-ju Uemon no Jo Fujiwara Muramasa saku." Thereafter, successive generations continued to use the same name. According to the prevailing view, the Bunki-era smith is regarded as the first generation, the Tenbun-era smith as the second generation, and the Tensho-era smith as the third generation. The Takeya Naomasa densho, bearing a colophon dated Keicho 17 (1612), records that Muramasa was also called Myodai and that three generations used the same signature. Of these, works considered to be by the second generation survive in the greatest numbers, display the highest technical level, and moreover exhibit tang signatures that are fluent and skillful in their manner of cutting. The lineage extended even into the shinto era, though the detailed divisions among later generations have not been firmly established.

The forging of Muramasa's works characteristically shows itame-hada mixed with mokume and nagare-hada, frequently tending toward hada-dachi, with ji-nie adhering and chikei entering. The hamon is typically a notare-based pattern mixed with large gunome, executed with deep nioi and thickly adhering ko-nie; kinsuji and sunagashi appear, and the nioiguchi is bright and clear. A defining hallmark of this smith is the conspicuous correspondence of the hamon on omote and ura, with the hatori on both sides precisely aligned. The valleys of the midare characteristically approach close to the cutting edge, and vigorous muneyaki is frequently present, at times producing an effect akin to hitatsura. The boshi is typically tempered deeply, often becoming ichimai-like in appearance, with a long kaeri that extends downward and continues into the muneyaki. First-generation works may be thought to have taken as their model the manner of the old master Go (Yoshihiro), displaying a bold style filled with spirited force, while the second generation's works show the most consistent excellence, with features such as hako-flavored tempering and a characteristically narrowed lower tang in the so-called tanago-bara form. Muramasa also excelled in the production of spears, with surviving omi-yari and katakama-jumonji-yari demonstrating abundant kinsuji and sunagashi within the temper even in polearm format.

Muramasa's oeuvre encompasses katana, wakizashi, tanto, and yari, all displaying a powerful and heroic character that distinguishes the Sengo line among late Muromachi smiths. At first glance the style can sometimes be confused with late Mino smiths such as Kaneshige, yet the precise alignment of the temper on both sides reveals a strong individuality. The finest works demonstrate a jigane of exceptional refinement with thickly adhering ji-nie and abundant interwoven chikei, paired with a hamon of bright nioiguchi and vigorous nie activity that together convey a magnificent, spirited force. The first-generation Muramasa's best works give the impression of surpassing even the second generation, while the second generation's most accomplished pieces combine bold tempering with a bright, clear nioiguchi and kenzen preservation of both ji and ha. The earliest dated katana of Bunki 1, bearing the smith's full signature with place of residence, common name, and year-date, stands as a document of high scholarly value for research on this lineage. Altogether, the Sengo Muramasa line represents one of the most distinctive and technically accomplished traditions of the late Muromachi period.