Yamaura Kiyomaro was born Naizosuke Tamaki in Bunka 10 (1813) at Akaiwa village in Komoro, Shinshu, the second son of the rural warrior Nobukaze and the younger brother of the smith Saneo. He learned forging under Kawamura Toshitaka, a swordsmith of the Ueda domain, signing first Masayuki and for a brief interval Hidetoshi, the name his teacher gave him, before returning to Masayuki within the year. Under the patronage of the bakufu retainer and military scholar Kubota Kiyone he went up to , forged for a year at in Choshu from the eighth month of Tenpo 13, returned to in Koka 2, and in the autumn of Koka 3 settled at Iga-cho in Yotsuya and changed his signature to Kiyomaro. He so excelled in the tradition that the published sources record he was called the Yotsuya Masamune (四谷正宗), and they place his reputation today as high as that of Kotetsu, calling him without question the foremost master among the . He died by his own hand at forty-two in Kaei 7 (1854).
What he aimed at, in the words of the published commentary, was the upper level of the transmission (相伝上位), and among smiths his construction and manner reveal with particular clarity. The temper is a mixed with , the entering, the thick and gathering coarse in clusters of , the whole work, as the puts it, filled with a vigorous and commanding spirit. Long and streaming run through most of his blades, in both the Masayuki and the Kiyomaro periods, the activity of a built on ; the published sources single out this play of and in his strong steel as splendid. The is , turning pointed with , at times thrusting up to a point or settling into a small round.
He forges an that flows and stands a little, well packed and at times mixed with large open grain, the laid thick and in fine particles, the entering frequently and the steel clear. Where the forging tightens into the only grows clearer. His mature carry an imposing shape, the body wide, the toward the point, the extended or running to a large point with the withered for a sharp impression.
The record now reads in two periods and a favoured register. The early Masayuki work is substantial: some twenty-six blades of the period, signed Masayuki, Minamoto Masayuki, Yamaura Masayuki, Yamaura Tamaki Masayuki and the bare single character Tamaki, dated from Tenpo 4 to Koka 3, among them the pieces inscribed 於萩城 and 於長門国 and the Komoro pieces inscribed 於信小諸城. The earliest, a Tenpo 4 bearing Kubota Kiyone's name, shows that the two men were already in contact during his Matsushiro years; the published sources note that its and are less abundant than in later work, though the is already bright. These blades carry a closely packed that often tends to , with a mixed with and pointed elements, deep and attaching . The mature Kiyomaro manner is the prime described above. Within it lies the register he prized most: the published sources say that 「志津伝は得意中の得意」, the transmission his forte of fortes, and they already read it in the early hand, calling a small Tenpo 11 a masterpiece of the manner. That register gathers in the and he favoured and in the , where a base mixed with and , with in clusters, tempers into a flamboyant .
What sets him apart from his contemporaries is this reach. He looked past the and Kotetsu copying of his day to the masters, taking Saburo Kaneuji as his model. His own steel and edge, thick in and , vigorous in , rich in and , are what the judges praise: they call one blade the very best among works by the same hand, and say of others that his true ability is there fully revealed. His Sai-jo rating in Fujishiro and the line named for him carry the -revival manner forward through his pupil Kiyondo and the wider Kiyomaro-.
Fujishiro grades him Sai-jo , and the Toko Taikan places him high among names. He has no National Treasures and no Important Cultural Properties; his record runs through the modern designation tiers, one blade at and sixty-eight at , with four blades also recognised before the war as , seventy-three designated works on record, every one of them signed. The published sources estimate his extant work at something over one hundred blades, note that examples in ordinary of standard dimensions are comparatively few, and call a matched dated Kaei 1 without parallel. The recorded blades pass through documented hands: the Iwasaki family and the Seikado Bunko, a retainer of the Matsushiro domain who ordered a , his patron Kubota Kiyone, Makino Suo-no-kami Yasushige, and the Bakumatsu swordsman Chujo Kinnosuke, whose favoured sword one is said to have been. Most are held rather than traded, so a or Kiyomaro reaches the market only from time to time and at the very top of it, and a signed example in private hands is among the more notable things a collector of could encounter.