"Both of us had an understanding that we should date someone we might one day marry", said Mako, the oldest of Emperor Akihito's four grandchildren.
M - Japan's Princess Mako has formally announced her engagement to a commoner after receiving the emperor's approval, BBCreported.
Announcing her engagement, Princes said that she felt "really happy" despite losing the royal status for Komuro, whose smile what she described look "like the sun".
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"Together with Mr. Komuro, I would like to make a warm and peaceful family that is full of smiles", she added.
The two first met in 2012 at a student exchange program information session held in a classroom at International Christian University in the Tokyo suburb of Mitaka, where they were both students in the same year. Both of them was in a long distance relationship while studying overseas, Mako in Britain and Komuro in the USA for one year.
The princess said she and Komuro call each other by their first names although she shyly declined to give "a live presentation". The official announcement was made in a news conference on Sunday by the Imperial Household Agency. Komuro, who is now working at a law firm while studying, proposed to the princess after dinner in December 2013.
A series of related rituals, including a betrothal ceremony (nōsai no gi), will be carried out before the couple's wedding, which is expected to take place in autumn next year at the earliest.
However, the happy news also bears with it the foreboding that it could spell disaster for the future of a royal family facing concerns about a declining population to keep their 2,600-year-old bloodline going. They announcement was originally planned for July, but they chose to postpone it following the heavy rains and flooding in northern Kyushu that month. Komuro and Mako will have to go through several more rites until the wedding, which will be 2018, the same year as her grandfather will relinquish the throne. Yet Crown Prince Naruhito has no sons, meaning that the succession would pass on to his younger brother Akishino, Princess Mako's father.