Nomura was born as the second son of a low-ranked " ashigaru samurai" in Hagi, Chōshū Domain, (currently Yamaguchi Prefecture). As a youth, he studied at Yoshida Shōin's "Shokansonjuku" academy, where he joined the Sonnō jōi movement against the Tokugawa shogunate and the increasing foreign presence in Japan. He participated in the unsuccessful assassination attempt against the "rōjū" Manabe Akikatsu and in the burning of the British legation in Edo in 1862. He fought as a member of the Chōshū armies against the Tokugawa during the Second Chōshū expedition.