Emperor Akihito's uncle, Prince Mikasa, who served in China during World War II and criticized the war waged in his older brother's name, was laid to rest Friday in solemn ceremonies attended by the Imperial family, Prime Minister Shinzo Abe and other mourners.

Mikasa's death at the age of 100 — the oldest Japanese royal in recorded history — leaves just four heirs to the Chrysanthemum Throne. The youngest brother of Emperor Hirohito, posthumously known as Emperor Showa, he was fifth in line to the throne.

His death comes amid renewed attention to the future of a monarchy whose past traditionalists say stretches back 2,600 years and whose future currently rests with one 10-year-old boy. Women cannot ascend the throne.