As it is well known, the imperial house of Japan is (still) facing a succession crisis. With male heirs to the throne in short supply for many years, the entire burden of producing a son is currently resting on a single youth, currently 20 years of age.
While there is no imminent pressure to reproduce for the young prince, the burden might be lessened quite a bit if the Succession Law were to be changed to absolute primogeniture, and women were allowed to ascend to the throne.
There are powerful arguments on both sides, and on the opposing one, one famous story is cited over and over again: That of Shōtoku, the 6th and last “real” Empress of Japan, and her involvement with a certain monk called Dōkyō.
Read the story, which is really nothing more than a juicy 8th century palace intrigue, over on Yamato, it’s a freebie!