Japan is celebrating news that Princess Kiko, wife of the emperor's second son, has given birth to a baby boy.
Japan got a first glimpse of its new heir to the throne on Friday as he left hospital in the arms of his mother, Princess Kiko.
The birth of a boy, the first in the imperial family for more than four decades, potentially resolves the country's succession crisis.
Prince Hisahito, who was born last Wednesday, is third in line to the Chrysanthemum Throne, behind Crown Prince Naruhito and his own father.
Women are not allowed to take the throne and the baby is the first boy born to the current emperor's children.
His birth was widely celebrated, as it headed off a succession crisis.
The baby becomes third in line to the throne, after Crown Prince Naruhito and his own father, Prince Akishino.
Only men are allowed to be monarchs in Japan, and Hisahito is the first new heir for four decades.
Both mother and baby were doing well, officials said.
Princess Kiko, the wife of the emperor's second son Prince Akishino, walked out of the hospital with her baby son in her arms, his forehead just visible above the blankets he was swaddled in.
Princess Kiko's pregnancy has attracted enormous media coverage.
"I am very grateful to the people, friends and family who prayed for the baby's safe delivery," Princess Kiko said, according to a statement released later by the Imperial Household Agency.
The 39-year-old princess, who is married to Prince Akishino, the emperor's younger son, already has two daughters.
"I am overjoyed by the birth and happy that today we are able to return home," she said.
For the waiting media and hundreds of proud Japanese, it was their first glimpse of the new prince.
She had been hospitalised since mid-August because of complications and gave birth by Caesarean section two weeks early.
Hisahito, whose name means serene and virtuous, slept as the smiling princess posed briefly for photographs with her husband.
Her son, born at 0827 local time (2327 GMT Tuesday), weighed 2,558 grams (5lbs 10oz).
Then the family was taken by car through streets packed with well-wishers, some shouting "Banzai", or long life.
Emperor Akihito and his wife, Empress Michiko, who are on a tour of Hokkaido, welcomed the birth.
Law change
"We would like to convey our sincere congratulations to the couple, who now face a happy day after quietly enduring the anxieties of the past 10 months," they said in a statement.
The baby's birth has averted a succession crisis in Japan. Emperor Akihito's eldest son, Crown Prince Naruhito, has just one daughter, and until Hisahito's birth, Prince Akishino and his wife had only two girls.
The birth has been particularly keenly anticipated because of debate over the succession issue.
Current Japanese law forbids women from ascending to the throne, and in recent years there have been calls for constitutional reform to change this requirement, to ensure the survival of the monarchy.
Japanese law forbids women from ascending the throne, but prior to the baby's birth there was no male heir among the emperor's grandchildren.
The proposal was backed by Prime Minister Junichiro Koizumi, who argued that it would make the succession process more stable.
Prince Akishino and his daughters went to visit Princess Kiko
But many Japanese conservatives were against the move, saying such a change would end centuries of tradition.
The present heir, Crown Prince Naruhito, and his wife, Princess Masako, have a young daughter, while any children born to Princess Sayako would not be eligible since succession can only go down the male line.
The debate was shelved when news of Princess Kiko's pregnancy was announced, but recent polls show that the Japanese public still backs the idea of a female monarch.
Japanese Prime Minister Junichiro Koizumi had been advocating constitutional reform to allow women to ascend the throne, but the debate, although supported by the public, was shelved when news of Princess Kiko's pregnancy was announced.
It is not clear where the debate, opposed by many conservative lawmakers, goes from here. Mr Koizumi said the birth was "good news", but did not comment further.
HAVE YOUR SAY Would it have been so bad to have changed the constitution to allow a woman to succeed? Pauline Fothergill, Halifax, UK Send us your comments Chief Cabinet Secretary Shinzo Abe, who is likely to become Japan's next prime minister, said the revision debate should continue in a "careful and calm" manner.
"Reforming the Imperial Household Law is an important issue that concerns the stability of the imperial family," he said.
Sword
Across Japan, many people were celebrating the birth.
Newspapers put out extra editions to cover developments and television stations broadcast special live programmes on the birth.
A small group of people gathered at the Imperial Palace to wave flags, while a troupe of women performed a traditional dance in the Tokyo district where Princess Kiko grew up.
While some were particularly pleased about the arrival of a boy, others were simply happy with a healthy baby.
"I guess it's a relief for the Japanese family that they wanted to have a boy," one man told the BBC. "But for me, I think, I guess I'm more girl or boy is okay. I don't think there should be such a fuss about it these days."
The baby will be named next Tuesday, seven days after his birth, by his father. Princess Kiko will choose a symbol to mark his belongings, according to tradition.
But first a messenger from the emperor is due to deliver a protective sword to the baby and place it on his pillow, Kyodo news agency reported.
