The 125th Emperor of Japan Akihito is going to abdicate the throne on April 30, 2019. The Crown Prince Naruhito is ascending to the throne. Since Naruhito does not have a son, but a daughter, the continued existence of the Japanese Emperor family has been worried about and questioned.
Not only the western mass media, but also some Japanese are arguing about the recognition of a female Empress. The Committee on the Elimination of Discrimination against Women, which is a United Nations treaty body, criticized Japan in 2016 because of not admitting a Female Empress.
Throughout Japanese history, 10 female Empresses reigned. They were either single or widowed. When a male successor was still too young or who would be the next heir to the throne had not been decided yet for various reasons by the emperor family members, female Empresses could temporarily ascend to the throne. The Emperors of Japan follow the paternal line, and this is the legitimacy of the Emperor of Japan. Applying the issues of discrimination against females by the United Nations is pointless. Furthermore, if the equality of females and males were demanded by the UN committee, the emperor family could rather insinuate the discrimination against men. In current times, a woman from a subject’s family is able to become the empress through her marriage to a prince, but not vice versa.
After the Second World War, the allied nations (in particular the USA) occupied Japan. One of their political measures limited and thereby diminished the Japanese emperor family. As a consequence, 11 families of close kin to the Emperor were declared common families. Should these families be reinstated as close kin to the emperor family, the paternal line may run on. Such cases existed throughout history and are not novel.
The Emperor of Japan must be a paternal successor; thus, the emperor is the Emperor of Japan. This has been so in the last 2678 years since the first Emperor ascended to the throne.