Japanese Princess Aiko, the daughter of Emperor Naruhito, on Wednesday turned 20, ready for a debut as a new adult member to take a share of official duties for the royal family whose population continues to shrink under the male-only succession law. 

Aiko is the only child of Naruhito and Empress Masako, a Harvard-educated former diplomat. She is currently studying Japanese literature at Gakushuin University, and says she is willing to help her parents by participating in royal duties. 

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“I would like to refine myself and move forward step by step so that I can grow into an adult who can be of service to others,” Aiko said in a statement released Wednesday by the Imperial Household Agency.

Aiko, whether she likes or not, is not eligible to ascend the Chrysanthemum Throne. Under Japanese law, she also has to leave her family if she marries a commoner, just like her older cousin, Mako, last month when she married her college sweetheart Kei Komuro. 

The 1947 Imperial House Law, which largely preserves pre-war family values, only allows male-line succession and forces female royal members marrying commoners to lose their royal status. 

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A government-commissioned panel of experts is discussing ways to stably maintain the royal family succession law. Many of its members are conservatives and have opposed female emperors, and suggested restoring now-defunct royal families to bring back their male descendants.

In modern history, when concubines were no longer allowed, the rule has caused the royal membership to keep declining, now down to 17. Naruhito has only two possible younger successors — his younger brother Akishino and his teenage son, Hisahito — except for his 85-year-old uncle, Prince Hitachi.

Hisahito is the only underage member of the graying royal family. 

On Sunday, Aiko will visit imperial family sanctuaries to offer prayers for their ancestors and gods, and will be formally recognized at a palace ceremony led by her father. She will also put on a formal dress and a tiara to greet her parents and grandparents. 

As a child, Aiko was known to be a big fan of Japanese traditional sumo wrestling and memorized the names of all wrestlers. Like her mother Masako, she is also known for love for animals.