Japanese Princess Mako, the eldest granddaughter of Emperor Akihito, and her longtime boyfriend Kei Komuro expressed delight Sunday at their engagement as they appeared before the public together for the first time.

"I am truly delighted," the 25-year-old princess said at a news conference held at an imperial residence on the grounds of Tokyo's Akasaka Estate.

Princess Mako and Komuro said they have dated for around five years since speaking to each other for the first time at a 2012 explanatory meeting for those planning to study abroad. At the time, both were students at Tokyo's International Christian University.

Komuro, 25, said he proposed in December 2013 after dining with the princess in Tokyo. He currently works at a law firm in the capital.

In the 10-minute press conference, the princess said both she and Komuro have been courting from the beginning with future marriage in mind. "Of course, I felt truly happy when he proposed and since my mind was already set, I accepted his proposal on the spot," she said.

Komuro said, "I sincerely recognize that I bear a grave responsibility" in marrying a naishinno princess -- a daughter or granddaughter of the emperor.

He added that he wants to create a "harmonious" family in which they can be themselves, vowing to do his best to achieve the goal.

The princess said Komuro "warmly encourages" her and that she was first attracted to his "smile that shined like the sun."

Komuro said the princess "quietly watches me like the moon" and that he was attracted to her as she is "a loving person with firm conviction."

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.

After the press conference, the princess and Komuro were scheduled to have dinner with her parents Prince Akishino and Princess Kiko, and his mother Kayo at the prince's residence Sunday night.