It's a new era in Japan, the Reiwa era. Emperor Naruhito has begun his reign as his father abdicated. It's a historic development, the first Imperial succession from a living Emperor in more than 200 years.
Emperor Naruhito is now the 126th Emperor of Japan.
Later on Wednesday morning, he'll take part in ceremonies at the Imperial Palace to mark his enthronement.
At 10:30 a.m., the new Emperor will take part in a ceremony to show he's inherited the Imperial Regalia, a sacred sword and jewel, as proof of his enthronement.
About 30 minutes later, he'll meet with representatives of the people. They include the Prime Minister, the heads of both chambers of the Diet, the Chief Justice of the Supreme Court, and local government leaders.