Yamaura Masao was born in Bunka 1 (1804) in Akaiwa village, Komoro, Shinano Province, the eldest son of the rural samurai Yamaura Nobukaze and elder brother of the celebrated Kiyomaro. Together with Kiyomaro, he studied under the Ueda domain smith Kawamura Toshitaka, signing early works as Kanri and Toshimasa before adopting the name Masao, then 'o, and finally Toshinaga in his later years. He used art names including "Tennenshi," "Yushaken," and "Yuunsai," and died in Meiji 7 (1874) at seventy-one.
His stylistic trajectory followed that of his brother: beginning with in the manner of Toshitaka, then shifting decisively toward . The consistently note a forging of with thick and conspicuous , and a tempering of mixed with , richly laden with , , and . His finest (, 58th Session) is described as possessing "a powerful forging -- thick with and heavily interwoven with " in which " and activities are richer than usual even for this maker's work." Yet the observes that "in comparison with Kiyomaro, his work tends to show fewer in the and fewer and within the hardened area, and the overall quality does not reach Kiyomaro's level."
Despite this candid assessment, Masao's designated works demonstrate a smith of real accomplishment, particularly in the mode where is vigorously expressed and his display the sharp profile he favored. His output spans both of bold construction and of refined character, and his commissions from named patrons attest to the regard in which he was held during the era.