Japan heralded on Saturday the coming-of-age of Prince Hisahito with an elaborate ceremony at the Imperial Palace, where a succession crisis is brewing. 

The nephew of Emperor Naruhito and second in line to become emperor after his father, the 19-year-old received a black silk and lacquer crown at the ceremony, which marks the beginning of his royal adult life.

"Thank you very much for bestowing the crown today at the coming of age ceremony," said Hisahito, clad in the traditional yellow costume for minors, bowing to Emperor Naruhito and Empress Masako, who smiled at him. 

"I will fulfil my duties, being aware of my responsibilities as an adult member of the imperial family," he told his parents at the ceremony in Tokyo, attended by a score of royal family members and relatives.

Hisahito was then seen boarding a carriage to attend other ceremonial events, after changing into a dark coloured costume, traditionally worn by adult royals.

Although the emperor has a daughter -- Princess Aiko -- the 23-year-old has been sidelined by the royal family's male-only succession rules. 

Even though tradition dictates only a man can carry on the imperial line -- which goes back 2,600 years according to legend -- opinion polls have shown high public support for a woman taking the throne. 

"It makes no difference to me whether a woman becomes the emperor or a man does," said Tokyo bartender Yuta Hinago.

The 33-year-old felt there could be "room for more flexibility" in the succession rules.

"Gender doesn't matter," part-time shop clerk Minori Ichinose, 28, told AFP, adding that she supports the idea of a female emperor.

Japan has debated the royal succession for decades, with a key government panel in 2005 recommending that it pass to the oldest child regardless of their sex. 

That appeared to pave the way for the emperor's daughter to rise to the Chrysanthemum Throne, but Hisahito's birth the following year silenced the debate. 

Politicians have been slow to act, "kicking the can down the road," and delaying a solution with youthful Hisahito in view, said Kenneth Ruoff, director of the Center for Japanese Studies at Portland State University. 

Traditionalists have asserted that the "unbroken imperial line" of male succession is the foundation of Japan, and major changes would divide the nation.

Under the post-war constitution, the royal family holds no political power. 

Pressure on women

With royal daughters forced to leave the family after marriage, one modernising proposal would see them continue their public duties after their nuptials. 

Conservatives, meanwhile, are pushing for the royal household to bring distant relatives back to the fold. 

But it is unclear if those men would be willing to give up their careers and freedom to continue the lineage. 

Hisahito said this year he has "not yet thought deeply" about his own marriage prospects, which could be challenging. 

Historically, women who wed royals have faced intense pressure to produce sons and some family members are regular subjects of online and media gossip.

Empress Masako, a former high-flying diplomat, struggled for years with a stress-related illness after joining the household, which some have put down to the pressure to have a boy.

Emperess Emerita Michiko, Naruhito's mother, also suffered stress-induced illnesses. 

Hisahito's sister, Mako, married her university boyfriend Kei Komuro. 

She has faced intense tabloid reporting over claims that Kei's family had run into financial difficulties, leading the former princess to develop complex post-traumatic stress disorder. The couple left for the United States, where they recently had a baby. 

Despite broad public support for changing the succession rules, away from the pageantry, people are focused on other issues, such as rising inflation, royal historian Hideya Kawanishi told AFP. 

"If people who are generally supportive (of women emperors) become a bit louder, then politicians can become more serious," said Kawanishi, an associate professor at Nagoya University. 

"But when ceremonies end, society, including the media, calms down and moves on."