Princess Mako, the eldest granddaughter of Emperor Akihito, and her longtime boyfriend Kei Komuro will meet the press together on Sept. 3 for the announcement of their engagement, the Imperial Household Agency said Thursday.

The announcement had originally been planned for July 8 but the couple decided to postpone it in the wake of damage brought by heavy rain that hit southwestern Japan prefectures earlier in the month.

The agency proposed that the princess and Komuro, both 25 years old, earlier this month set another date for the announcement, while confirming reconstruction efforts in the devastated areas, according to the agency.

The new announcement day was fixed after the adjustment of schedules for the emperor, Empress Michiko, and the princess's parents Prince Akishino and Princess Kiko.

Princess Mako and Komuro met five years ago when they were both students at International Christian University in Tokyo, and Komuro reportedly proposed about a year after they started going out. He currently works at a law firm in the capital.

On the morning of Sept. 3, the emperor is expected to carry out a procedure to approve their marriage. Agency chief Shinichiro Yamamoto will then hold a press conference to announce the couple's engagement after reporting to the emperor and empress, as well as the princess' parents, that he would make the announcement to the public.

It will be the first time for Princess Mako and Komuro to meet the press together.

Their engagement will be formalized through a traditional rite of betrothal called "Nosai no Gi." It will be followed by a number of ceremonies in the run-up to their wedding expected for 2018.

In the case of the emperor's daughter Sayako Kuroda, her engagement announcement was delayed twice due to unexpected events.

The agency originally planned to announce her engagement to Tokyo metropolitan government employee Yoshiki Kuroda in November 2004. But it was postponed to Dec. 18 after a huge earthquake struck Niigata Prefecture. Then Princess Takamatsu, the emperor's aunt, died early on that day, so the engagement announcement was pushed back further to Dec. 30.

The last marriage of a Japanese princess took place in October 2014 when Princess Noriko, a daughter of Emperor Akihito's late cousin Prince Takamado, tied the knot with Kunimaro Senge, the eldest son of the chief priest of Izumo Taisha, a Shinto shrine in Shimane Prefecture.

Princess Mako's marriage would be the first of a naishinno princess, a daughter or granddaughter of the emperor, since Sayako Kuroda's wedding in 2005.

Japan's parliament enacted a law in June to allow the 83-year-old emperor to pass the throne to his elder son Crown Prince Naruhito in what would be Japan's first abdication in two centuries.

The timing of the abdication has yet to be determined, but after the handover of the Chrysanthemum throne, Prince Akishino, Princess Mako's father, is set to become first in line to the throne.

Princess Mako is scheduled to travel to Hungary with Prince Akishino from Saturday on a private trip.