黑船來航
After completing a thorough education in literature, art, and military training, Nagai entered the ranks of the Tokugawa bureaucracy. He served from 1851 to 1852 as an instructor at the "Kitenkan", a branch of the Shogunate's "Shoheizaka" academy, located in Kōfu, Kai Province. Shortly after the arrival of the Perry Expedition challenging Japan national isolation policy, Nagai was appointed as a "metsuke" and was placed in charge of casting new cannons for coastal defense.