Komuro said they kept in touch even though they were physically far from each other.
"First I was attracted by his bright smile", Princess Mako told a press conference.
Under a controversial Japanese law female imperial family members forfeit their status upon marriage to a commoner, whereas male members do not. 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.
She also said her love is "a honest, strong-minded, hard worker, and he has a big heart".
'Having a family still goes beyond my imagination, but I hope to make one that is warm, comfortable and filled with smiles, ' Mako said. "While I worked to help the emperor and fulfil duties as a royal family member as much as I can, I've been cherishing my own life".
Kei Komuro, Princess Mako's fiance, described her as someone who quietly watches over him "like the moon".
Mako graduated from ICU in 2014 with a Bachelor's degree in Art and Cultural Heritage. Princess Mako has a master's degree from the UK's University of Leicester and is now a researcher at a museum.More news: Watch Jordan Vogt-Roberts' Destiny 2 Trailer
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Komuro was dubbed as the "Prince of the Sea" in 2010 while serving as a tourism promoter for the city of Fujisawa.
The news of their engagement was reported in May by the Japan Times and later confirmed by the Imperial Household Agency.
Mr Komuro is studying business law and works at a law firm. They announcement was originally planned for July, but they made a decision to postpone it following the heavy rains and flooding in northern Kyushu that month.
While the couple have officially announced their relationship, their engagement will become official only after a traditional rite of betrothal called Nosai no Gi takes place, Japan Times reports.
Komuro, 25, added that he is also thankful to Mako's parents, Prince Fumihito and Princess Kiko, as well as many others for warmly allowing their courtship over the years.
Princess Mako's 83-year-old grandfather, Emperor Akihito, is expected to abdicate next year - Japan's first abdication in two centuries.
Princess Mako came of age in 2011 and was assumed her official title of Grand Cordon of the Order of the Precious Crown.