Twelve-year-old Hisahito, son of Crown Prince Akishino, is second to the Chrysanthemum Throne when Akishino's older brother Naruhito inherits the crown from his father on May 1.
Akishino becomes his first in line, but already 53.
"The entire future of the imperial family depends on a young boy – that he will stay healthy and be ready to marry children with his wife and children have, "says Ben-Ami Shillony. Professor of Japanese at the Hebrew University in Jerusalem.
Conservative and patriarchal Japan excludes women who make up 13 of the 18 members of the royal family from accession to the throne. This was not always the case.
Empresses dominated Japan at various times over several centuries until they were closed in 1889.
Archeological studies of tombs show that female leaders dominated Western Japan According to Chizuko T. Allen, a historian at the University of Michigan, in the fourth century.
While the tradition of female rulers and chiefs was commonplace in ancient Japan, Shillony says that history books tend to emphasize the art of male emperors.
"Even though the female Empress has achieved many things, they are still not considered as outstanding as the male emperors," he says.
Some historians claim that the Empresses were merely puppet rulers who abdicate when a suitable male heir came of age. Others say that they shaped Japanese history more than their male counterparts.
"From today's point of view, it is interesting to think how the contribution of the empresses of Japan in the past to the history has so dwindled," says the historian of the University of Michigan, Hitomi Tonomura.
"By completely ignoring these women or interpreting their role as mere" fillers "between (imperial) men, Japanese society offers no historical idea of what women can and do."
With the Modernization of Japan During the Meiji era from 1868 to 1912, the then leaders changed the role of the Emperor and reinstated him as military commander-in-chief. –
Since a woman could no longer command the military, the Meiji leaders believed it would not make sense to have ruling female empresses, Shillony says. An exclusively male succession was established.
The desire to recreate the West was also strong.
The leaders of Meiji were inspired by the Prussian constitution – which forbade women to ascend the throne – and in 1889 forbade women to be enthroned, Shillony says. They did not want to repeat the British model in which Queen Victoria ruled.
Instead, the period saw a masculinization of the emperor and Japanese society in general, while the Meiji regime emphasized the perceived superiority of men over women.
"In the Meiji Constitution is the term" ie "(House) It was enrolled – these subordinate wives and household members under a patriarch – this was not the case before," says the historian Tonomura.
The US occupation after Japan's defeat in World War II brought society into society with the slow introduction of American values.
"The US did not want to alienate the Japanese establishment by degrading its status as an emperor," Shillony says. "People believed that the issue of sex in the imperial family should be addressed by future governments."
Graphics by CNNs Jason Kwok and Natalie Leung.