With Japan's Emperor Akihito set to abdicate on April 30, 2019, the focus will likely shift to Crown Prince Naruhito, who will ascend the throne, and Crown Princess Masako, who has long been in a battle with depression.

While the elder son of the 83-year-old emperor looks certain to breathe fresh air into the world's oldest hereditary monarchy, scholars and royal watchers expressed caution over the increased burden and added public attention on the crown princess, who is still recuperating from stress-induced illness.

At a press conference on his birthday in February, the 57-year-old crown prince said, "I want to pursue the desirable shape of the imperial household sought in accordance with (changes in) each generation."

His message suggested that he stands ready to take the Chrysanthemum throne and add his own colors to the imperial household, scholars said, adding that they expect him to play a greater role in addressing international issues.

As a former career-track diplomat, the Harvard-educated crown princess is seen as the best supporter for the crown prince assuming such a role, they said.

"Emperor Akihito has worked hard to heal the scars of World War II and support vulnerable people. The crown prince is likely to continue some of those tasks," said Hidekazu Kanda, a journalist covering the imperial household.

But the new emperor's activities "will likely encompass more of an international agenda as he has shown keen interest in such issues as conservation of water, environment and animals," said Kanda, also a part-time lecturer at J.F. Oberlin University.

Just as the current emperor and Empress Michiko often kneeled down and offered words of comfort during their visits to disaster-hit areas, the new imperial couple will most likely inherit the same attitude and demonstrate their eagerness to be together with people, observers said.

Midori Watanabe, a visiting professor at Bunka Gakuen University, said it would be important for the new emperor and empress to together meet the public and "display an image of a happy family."

"Princess Masako seems to be making efforts to prepare herself to assume such a role as she has been appearing in public more often over the last couple of years," Watanabe said.

But concerns remain over to what extent Crown Princess Masako will be able to fulfill such expectations when she becomes empress, as the crown prince said earlier this year that his wife's conditions still have "ups and downs" and that he hopes she will engage in more activities "carefully and gradually."

In 2004, the Imperial Household Agency announced the crown princess was diagnosed with adjustment disorder after she cancelled her official duties the previous year following a bout of shingles.

The imperial household has been exposed to media speculation of a family rift, especially after the crown prince said in May 2004 in relation to his wife, "It is true there were developments that were regarded as denying her career and going against her personality."

The 53-year-old crown princess, a commoner like Empress Michiko, gave up her career to enter the imperial family in 1993 after accepting a marriage proposal by the crown prince, having initially declined the offer.

She gave birth to her only child, Princess Aiko, in 2001, but continued to receive pressure to produce a male heir as Japan's current law stipulates that only males born to the male lineage of the imperial family can ascend the throne.

"The immense pressure to bear a male heir must have been one of the major causes of her illness" until Prince Hisahito was born to Prince Akishino, the younger brother of the crown prince, and Princess Kiko in 2006, said Hideya Kawanishi, an associate professor of Japanese modern history at Kobe College.

The crown princess had shunned notable public appearances for roughly a decade but in 2013 she visited the Netherlands to attend the coronation of Dutch King Willem-Alexander, making her first official overseas trip in 11 years. In 2014, she attended a banquet at the Imperial Palace for the first time in 11 years.

In recent years, she has engaged in various official duties including a visit to Tonga in 2015. In the year through her 53rd birthday on Dec. 9, 2016, she took part in 57 public duties and imperial rites that required her to go out of her residence, the highest number since 2010 when such data became available.

Such a trend indicates signs of improvement, but Kawanishi expressed caution as the crown princess' burden is expected to increase after her status is raised.

Although a simple comparison cannot be made, Empress Michiko attended 338 official duties, excluding imperial rites, in the year through her 83rd birthday on Oct. 20 this year.

"For sure, she will also be thrust into more public exposure after becoming empress," said Kawanishi, adding that that increased attention could negatively affect her health conditions.

In the early period of the current Heisei era that began in 1989 with the reign of Emperor Akihito, Empress Michiko suffered from psychogenic aphasia due to public backlash against the way the imperial couple performed their duties.

Criticism was leveled against the empress with some Imperial Household Agency officials yearning for the traditional styles of the Showa era (1926-1989) under the reign of Emperor Hirohito, posthumously known as Emperor Showa. In modern Japan, an era name is used for the length of an emperor's reign.

Imperial household watchers said they fear similar things might happen again.

"Empress Michiko actively engaged in many duties, but the duties of empresses reflect their personalities and characters. So we, the general public, should not demand too much or the same thing from Crown Princess Masako. Otherwise, it would be too tough for her," said Kawanishi.

Scholars said the Heisei era has seen a significant rise in the number of public duties performed by the imperial family. As the public largely supports such activities, slashing the workload would not be so easy despite the shrinking size of the imperial family that has even raised concern about a possible succession crisis, they said.

If Crown Princess Masako is not able to fully perform her duties after becoming empress, her tasks could be shared by other imperial family members. But the number of family members, now 19 including the retiring emperor, is expected to drop further as women lose their status after marrying commoners.

Princess Mako, 26, the eldest granddaughter of Emperor Akihito, is set to leave the imperial family after her scheduled marriage to her former university classmate in November next year.

Woes are also lingering over a stable imperial succession as 11-year-old Prince Hisahito is the only male of his generation in the imperial household. But no major steps have been taken to address the issue.