Shimazu Nariakira
Atsuko was thought to have been sent to Edo Castle with the aim of helping Shimazu Nariakira politically. The question of the next heir to the shogunate was divided between the choice of Tokugawa Yoshinobu, then head of the Hitotsubashi-Tokugawa house and Tokugawa Yoshitomi, then head of Kii-Tokugawa house. In order to ensure that Yoshinobu became the next in succession, Atsuko was arranged to wed into the Tokugawa clan.