Princess Kasuga no Yamada

Princess Kasuga no Yamada was Empress of Japan as the consort of Emperor Ankan.
She was the daughter of Emperor Ninken and was married in 513. Before the ascension of Emperor Kinmei, Kinmei recommended that Princess Kasuga no Yamada become the empress regnant herself. The empress consort declined this however and Kinmei himself succeeded.
According to the Nihon Shoki, Emperor Kinmei did not want to succeed to the throne as he felt he was too young, adding that Princess Kasuga no Yamada had "a clear acquaintance with all matters of administration". She rejected this offer stating
If this had happened, and assuming that this encounter was true she would have become the first historically verifiable female emperor of Japan. Due to her declining, it would be Kinmei's own daughter, Empress Suiko in 592, that would become Japan's first female emperor.