Atsuko was thought to have been sent to Edo Castle with the aim of helping Shimazu Nariakira politically.

In order to ensure that Yoshinobu became the next in succession, Atsuko was arranged to wed into the Tokugawa clan.

Following the demise of her husband, Atsuko took the tonsure, becoming a Buddhist nun, and took the name Tenshōin on 26 August 1858, and she was given Junior Third Rank.

In 1862, as part of the Kōbu Gattai ("Union of Court and Bakufu") movement, Iemochi was married to Imperial Princess Kazu-no-Miya Chikako daughter of Emperor Ninkō, and younger sister of Emperor Kōmei.

During the Meiji Restoration, Tenshōin and her daughter in law, Seikan'in (Kazu-no-Miya's name after tonsure) helped negotiate for the peaceful surrender of Edo Castle.