Prince Hisahito turns 20 as Japan's government reinforces male-only succession rules

Prince Hisahito, the 20-year-old nephew of Emperor Naruhito, celebrated his birthday on Sunday amid increasing interest in his potential future role as Japan's monarch. The younger of the 16 members in Japan's aging imperial family, Hisahito is the second in line to the 1,500-year-old Chrysanthemum Throne. A biology student at the University of Tsukuba near Tokyo, the prince, known for his love of animals and particularly dragonflies, has recently taken on some official duties.

In May, Hisahito attended a palace banquet in honor of Philippine President Ferdinand Marcos Jr. Later that year, he prayed for the victims of the atomic bombing in Hiroshima and participated in a summer camp for teenagers in a southwestern Japanese city. While primarily focused on his studies, Hisahito's increased visibility as a potential future emperor has drawn attention.

Comparisons have been drawn between Hisahito and his popular cousin, Princess Aiko, who turned 24 in May. The 20-year-old prince, who often bikes around campus or carries a bug-catching net, is seen as the youngest member of the shrinking imperial family.