箱館戰爭
Nakamuta was born in Saga domain (present day Saga prefecture). He was a samurai-sailor in the domainal navy, which later became the core of the fledgling Imperial Japanese Navy. During the Boshin War to overthrow the Tokugawa bakufu, Nakamuta was captain of the frigate "Chōyō" at the Naval Battle of Hakodate. The "Chōyō" exploded after being hit by the rebel ship "Banryū", but Nakamuta survived.