She was the eighth and youngest daughter of Emperor Ninkō and his concubine, Hashimoto Tsuneko – renamed Kangyō'in (観行院) after she took the tonsure.

Under pressure from her family, unwilling to be responsible for Emperor Kōmei's abdication and threatened with the monastery, Princess Kazu finally agreed, but gave several conditions including demands that her lifestyle in Edo would remain the same as in Kyoto and that she would be able to return to Kyoto on the anniversaries of her father's death.

Due to concerns over attacks by those against the Tokugawa shogunate's policies, security forces from dozens of hans were mobilised to protect the procession.

This ceremony differed from that of all previous Tokugawa shōguns: having been made a naishinnō by her brother before leaving Kyoto, Kazu now outranked her husband as well as her mother-in-law, Tenshō-in.

Furthermore, Princess Kazu retained the customs of the Imperial palace, which caused considerable friction with Lady Tenshō-in.

However, she apparently enjoyed such a good relationship with her husband that they are usually called the closest couple out of all the Tokugawa shōguns, and Iemochi only once took a concubine, which the princess gave him permission to do.

Eventually Tenshō-in would reconcile with Princess Kazu, and the bakufu submitted to her order to address her as "Kazu-no-Miya-sama", as opposed to the traditional "Midai-sama".

She became a Buddhist nun, receiving the title of Seikan'in-no-miya (静寛院宮)[1] on 9 December 1866, but just a few weeks later her brother Emperor Komei would also pass away.

During the Meiji Restoration, Seikanin and Tenshō-in helped negotiate for the peaceful surrender of Edo Castle by restraining extremists of both sides.

[citation needed] The exhumation of Princess Kazunomiya's remains, together with the story of the mysterious fading photograph that was found with her, was referenced in Yasunari Kawabata's 1961 novel Beauty and Sadness.