尊王攘夷
Sumihiro was an active ruler, interested in both "rangaku" and classical learning, and concerned with the direction the country was taking into the unsettled Bakumatsu period. In 1862, he formed an alliance with neighboring Hirado Domain. Sumihiro was considered a strong Tokugawa loyalist, and in 1863 was entrusted with the important position of Nagasaki bugyō, but defected after only a year to become a supporter of the "Sonnō jōi" movement.