尊王攘夷
Shinagawa was born in Hagi, in former Chōshū Domain (present day Yamaguchi Prefecture). His father was an "ashigaru", or lower ranking foot soldier in the service of the Mōri clan. During the Bakumatsu period, he attended Yoshida Shōin’s Shoka "Sonjuku" Academy, and was a fervent supporter of the "Sonnō jōi" movement. In 1862, together with other pro-"Sonnō jōi" Chōshū samurai, he was a participant in an attack on the British legation in Edo. He was also present at the unsuccessful Hamaguri rebellion in Kyoto in August 1864. During the Boshin War of the Meiji Restoration, he served as a staff officer in the Imperial armies in various battles against the remnants of Tokugawa shogunate forces in the Ōuetsu Reppan Dōmei in northern Honshū. He is also credited with writing the lyrics of ""Miyasan, Miyasan" (宮さん宮さん), also known as "Tonyare-Bushi"", a humorous loyalist song that was popular during the Boshin War.