The Japanese royal family has been dogged with controversy as women are not allowed to retain their Imperial status after marriage or ascend the throne, whereas male members can.
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".
Komuro, in response, said Princess Mako "has been quietly watching over me like the moon".
'Having a family still goes beyond my imagination, but I hope to make one that is warm, comfortable and filled with smiles, ' Princess Mako said. The couple met as students in 2012 at Tokyo's International Christian University.
The couple had a long-distance relationship while studying overseas - Princess Mako in Britain and Mr Komuro in the US - for one year.
The engagement to Kei Komuro, who works in a Tokyo law office, comes after Japanese lawmakers in June approved a bill to allow Akihito to step down, the first abdication by a Japanese monarch since 1817.
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Sacrificing her royal status just for love, Japan's Princess Mako has publicly declared her engagement to a common man.
With regards to the proposal, it was also revealed that Komuro proposed after dinner one evening of December 2013.
The formal announcement came from Japan's Imperial Household Agency on Sunday, after local media reported news of the planned engagement in May. But due to the unfortunate torrential rain that flooded northern Kyushu that month, the royal family chose to postpone the announcement. They both are 25 years old.
According to NHK, the wedding between the Princess and Komuro is expected to take place next year.
Japan's Princess Mako got engaged to a commoner on Sunday. This has a great difference for the males, as the law states that princes' who marry commoners will retain their royal title. The royal family last wedding ceremony saw Princess Noriko of the Imperial family marry Kunimaro Senge, the eldest son of the chief priest of Izumo Taisha, a Shinto shrine. Her younger brother, Prince Hisahito, is the third in line to the throne after their uncle, Naruhito, Crown Prince of Japan, and their father.