Prince Hisahito, the only son of Prince Akishino and Princess Kiko, celebrated his fourth birthday on Monday.
Prince Hisahito, third in line to the Chrysanthemum Throne after Crown Prince Naruhito, Emperor Akihito's eldest son, and Prince Akishino, the Emperor's second son, attends the kindergarten linked with Ochanomizu University in Tokyo.
At home, Prince Hisahito enjoys riding a bicycle with training wheels once used by his elder sisters — Princess Mako and Princess Kako, the Imperial Household Agency said.
