Japan formally proclaimed Crown Prince Akishino - younger brother of Emperor Naruhito - first in line as heir to the throne today.
Naruhito became monarch last year following their father's abdication.
The day-long ceremonies at the palace had been scheduled for April but were postponed because of the coronavirus pandemic.
Under Japanese law, only males can inherit the throne, so Emperor Naruhito's only offspring, 18-year-old Princess Aiko, is ineligible.
This meant that Crown Prince Akishino, also known as Fumihito, became heir to the oldest continuing hereditary monarchy in the world - Japan's Chrysanthemum Throne.
Moves to amend the law barring females from the line of royal inheritance lost steam when Akishino's wife, Crown Princess Kiko, bore a son, Hisahito, in 2006. The couple already had two daughters.
"I deeply ponder the responsibility of Crown Prince and will discharge my duties," said Prince Akishino, wearing flowing orange robes.
Akishino, 54, is one of just three heirs to the throne along with Hisahito, 14, and Prince Hitachi, 84, the younger brother of Emperor Emeritus Akihito, who stepped down last year in Japan's first abdication in two centuries.
Changes to the succession law are anathema to conservatives, but debate over how to ensure a stable succession is likely to intensify.
One option is to allow females, including Aiko and Hisahito's two elder sisters, to retain their imperial status after marriage and inherit or pass the throne to their children,a change that surveys show most ordinary Japanese favour.
Conservatives want to revive junior royal branches stripped of imperial status after the war.
