Concerns persist over the stability of Japan's imperial succession, as the 1947 Imperial House Law stipulates that only males of the patrilineage can ascend the throne.
Emperor Naruhito and Empress Masako have a daughter -- Princess Aiko, 17 -- and there are other females in the imperial family, but the Imperial House Law requires women to abandon their imperial status after marrying commoners.
The group's ideas include having unmarried male members of the former branches join the imperial family through adoption or marriage, if they want to.
Emperor Naruhito officially proclaimed his enthronement in an ancient-style ceremony last Tuesday before some 2,000 guests, including dignitaries from about 190 countries and international organizations.
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