The published sources open his record with the old texts: the Genki Mekikisho and the Kokon Meizukushi divide the swordsmiths of into the smiths and the Senoo smiths, and where the line customarily carries the character tsugu (次) in its signatures, the Senoo line, derived from the founder Noritaka, does not use it. Masatsune is the representative smith of this Senoo group, active from the end of the period into the early period. The forge stood on the lower reaches of the Takahashi river, east of the site and toward , a place one paper records as opened by the Taira retainer Senoo Taro Kaneyasu, and the cites this geography, together with the likeness of the work itself, to explain the cast of his manner. The smiths around him, Koreshige, Yasuie, Hirotsune, Tsunezane, Moritsune and Yukizane, survive almost nowhere, so the Senoo school is known today essentially through his blades; of those, the sources note, the surviving examples "are not particularly few". The older papers filed the very man as the Masatsune, and only the more recent designations title him Senoo, a shift in filing that is itself part of his scholarship.
His keep the grace of their era. Blade after blade is described as slender, deeply curved at the and closing in a small , "a classical and elegant that does not descend below the early period". Over this form runs a in shallow , mixing , and . and enter well, and fine attaches overall. In places the edge frays into , with and working through. The continues into a , or finishes near , lightly brushed with . He signs only the large two character , cut with a thickish chisel, and the published record notes as a peculiarity of the name that examples exist with the characters on the and on the both ways. Twelve signed blades stand on his record, and the published sources repeatedly mark the signed state itself as "precious as research material".
The is where his province declares itself. The forging is to itame with mixed in, thick in , with fine entering; appears, and at its fullest the takes on the crepe-like quality the sources call , over which a faint can stand. The states the marks of his country as a formula: "the presents a texture, appears, and the become , and in these points the marks of the smiths are shown". The temper of the whole nevertheless leans east. The old transmission texts already record of the Senoo work that it "resembles things", more in spirit than the mainline, and the Bijutsuhin compiler, before a deep with , finds the man himself in the crowding of the temper: "the enter thickly, showing this smith's character well".
The scholarship around the name is layered. The signatures vary enough that, the published sources repeat, the name does not appear "limited to a single smith", and some connection with the Masatsune of neighboring is suspected from geography and style alike, a question the expressly leaves open for further study. The filing itself has moved with the scholarship: the designations of the 1960s through the 1980s title his blades , those from the 1990s onward and then Senoo, as the school's separate identity firmed. One case shows the old connoisseurship crossing the line between the two names. To a of his, "in Genbun 5 Koyu appended an attributing it to Masatsune"; examined today, the writes, the is "a state close to the so-called , with mixed in" and the original are clearly , so that "it is appropriate to judge it as the Masatsune of the Senoo line". A , for the rest, is an exception in his work: the Bijutsuhin text remarks of the single carrying a that this is "rare for Masatsune".
The heart of his connoisseurship is the namesake problem, two smiths called Masatsune working at almost the time in adjoining provinces. The published sources state it without evasion. Blade after blade is introduced as showing "at first sight a workmanship closely approaching Masatsune"; next to the contemporary pieces, they concede, many of his works carry "a somewhat more austere flavor", while "among them are examples that leave almost nothing to choose". Style alone, in other words, does not decide between the two, and the decision rests on his own marks. The texts give the rule plainly: "compared with , most show a slightly subdued, and a that stands somewhat is general", and there, they write, the slight individuality of work shows. To this the adds the -laden, -like quality of his , and the adds the decisive mark, an original unmistakably , the very point on which the set aside the old Honami .
Fourteen designated works stand on record, among them three and five blades together with five Bijutsuhin. Fujishiro rates him Sai-jo , and the Toko Taikan sets his value at 2,500. Seven of his blades carry recorded provenance. One is recorded as the sword worn by the Sengoku general Satake Yoshishige, passing in the later period to the Kikkawa, a bakufu retainer house, and a with folded back signature descended in the Date house of Sendai. His designated blades sit in the , and Bijutsuhin tiers, so the record is not closed to private hands, and of recorded whereabouts his blades rest almost entirely in private collections; even so, one comes to market only rarely. What a collector may realistically encounter is a signed two character of the end of or the opening of , of the kind the judged "an unmistakably archaic piece, its and carrying a moist quality, of high dignity", and the appearance of one is an uncommon event.