The line begins with a man. The record that no Kami Masatsune (政常) was born at Nōdo in Province, where he first signed Kanetsune (兼常) and is variously said to have been the son or a disciple of Kanetsune of Seki. In Eiroku 10 (1567) he established an independent branch line and moved to Komaki village, likely changing his name to Masatsune about that time; in the fifth month of Tenshō 19 (1591) he received the court title no Kami, and in Keichō 5 (1600) he followed Matsudaira to Kiyosu in Owari, where he became a retained smith (kakae-kō) of the Owari Tokugawa house. Several records place him at Kiyosu alongside Hōki no Kami Nobutaka and Hida no Kami Ujifusa, the three later counted as the Owari Sansaku (Three Smiths of Owari). After taking the tonsure and retiring in Keichō 12 (1607), he passed the name to his son; when that second generation died suddenly two years later he resumed forging under the nyūdō signature Masatsune Nyūdō, and is said to have died in Genna 5 (1619) at the age of eighty-four. A separate second generation, no Kami Fujiwara Masatsune, is recorded as the son of Daidō of Gifu, adopted into the line, who carried on its spear and work.
A foundation worked toward defines the shared hand. The forging is mixed with , frequently flowing into toward the and , with the grain standing somewhat (), abundant , and ; a -like feature rising from the is noted on several and . The temper that the call his specialty is a chū- to broad in , the worked with , , , and uchi-noke, with and mixed in, fine and running through, and a bright . Beside this restrained mode runs a bolder of and with , sometimes or , where the grows coarse and clustered and the turns (subdued); the Owari-Seki "wet" quality appears in the wider blades. The tends to straight with and in the works, with a rounded or long return in the works. Carving is plain but crisp: , , , with , and the rarely seen no in openwork.
Among extant works, the agree, and are the most numerous and of high skill, and are comparatively common with the spears often sasaho form, while and are extremely few. For this rarity gives weight to the long swords: the 67th Kanetsune-signed , dated by its and large to about Eiroku, anchors the smith's early phase, and the 31st Masatsune Nyūdō shows the flowing , shallow , and read as his own. Named pieces include the no Kami Masatsune Nyūdō held by the Imperial Household Agency and the once with Tokugawa Iesato and the Reimeikai Foundation; one survives in akikusa- with fittings by Mogarashi Sōten of Hikone. The note that in his bolder work Masatsune looked to the masters Sadamune and while keeping the and traces of his root, placing his line as the Owari channel through which the - passed into .