The groom-to-be is a prince himself ... of sorts.
The Imperial Household tells CNN plans are underway for the 25-year-old princess, granddaughter of Emperor Akihito, to become engaged to Kei Komuro, also 25, a law firm worker and graduate student who once starred in a tourism campaign as "Prince of the Sea."
The couple met five years ago as students at the International Christian University in Tokyo, Japan's national broadcaster NHK reported.
It was while in university that Komuro played the "Prince of the Sea" in a beach tourism campaign for the city of Fujisawa, south of Tokyo.
Shrinking imperial family
Japan's centuries-old imperial law requires a princess to leave the imperial family upon marriage to a commoner.
The last to do so was Princess Mako's aunt, Sayako, the only daughter of Emperor Akhito, when she married town planner Yoshiki Kuroda in 2005.
The engagement won't become official until a ceremonial exchange of gifts, but the news has reignited concerns about the shrinking size of the imperial family, which currently has 19 members, 14 of whom are female.
Imperial law only allows the throne to be passed to male heirs, of which there are only three: Crown Prince Naruhito, his younger brother Crown Prince Akishino, and Akishino's son, Prince Hisahito.
In addition to Princess Mako, there are six other unmarried princesses -- who will also lose their royal status if they marry commoners. That has raised the possibility that the imperial family will not have enough members to continue carrying out its public duties.
Future of the monarchy
Last summer, 83-year-old Emperor Akihito voiced concerns that his advanced age
may begin to affect his ability to rule.
Akihito said that while he felt he was in good health he was worried about the increasing burden of the role.
"When I consider that my fitness level is gradually declining, I am worried that it may become difficult for me to carry out my duties as the symbol of the State with my whole being as I have done until now," he said.
His announcement followed one from the Imperial Household a few months earlier that he and Empress Michiko, 82, would reduce their public appearances.
Imperial law requires an Emperor to serve for life, but Akihito's announcement put plans into motion for the Japanese parliament to allow the Emperor to step aside should he choose to. The draft bill for the Emperor's abdication is to be submitted for both the upper and lower houses of parliament this week.
'Prince of the Sea'
On Wednesday, Japanese media focused on the man who has stolen Princess Mako's heart.
Journalists camped out in front of the law offices where Kei Komuro works as a paralegal.
Komuro declined to answer questions about the impending engagement, telling reporters, "I would like to talk about it when the time comes."
Japanese citizens also wanted to find out more about Komuro, flooding the Fujisawa City Ocean Prince website, local media reported.
Reactions from the public have so far been generally positive, but some are wondering what the upcoming marriage will mean for the future of the monarchy.
"I personally think a female imperial member should be allowed (to remain in the family)," said Meiko Hirayama, a 44-year-old employee at an accounting firm. "I guess the male line of succession would be kept through the crown prince and his brother, but I think there should be no problem that there could be a female emperor someday."
But 71-year-old Katsuiji Tsunoda insisted the heir to the throne exclusively be male.
"It's a tradition that has continued for over a thousand years. If we go with the global trend, anyone could be the emperor," he told CNN. "We must respect tradition."