Preparations are under way for the abdication of Emperor Akihito of Japan on 30 April 2019. One question that naturally has arised is what to call them afterwards.
Last week The Japan Times wrote, with the Imperial Household Agency as the stated source, that Emperor Akihito will be referred to as «Emperor emeritus», while his wife, Empress Michiko will use the title «Empress emerita». The Japanese equvialents will be jōkō (上皇) and jōkōgō (上皇后) respectively.
The similar practice in Europe varies. While the Dutch monarchs traditionally reverts to the title of prince or princess* following abdication, King Juan Carlos of Spain, King Albert of the Belgians and Grand Duke Jean of Luxembourg are still titled King or Grand Duke respectively, but they are of course not HM The King or HRH The Grand Duke anylonger. A parallell to Japan would be the Roman-Catholic Church, where Pope Benedixt XVI is referred to as «supreme pontiff emeritus».
* The three monarchs prior to King Willem-Alexander were all women – Queen Wilhelmina, Queen Juliana and Queen Beatrix respectively – and they all reverted to the title of Princess of the Netherlands following their abdication. I mention the title prince the just for «the sake of balance and equality» and because I expect that King Willem-Alexander will use the title of Prince again if he should decide to abdicate some time in the future. As far as I know, the first King of the Netherlands, Willem I, continued to use the title King following his abdication in 1840.