The pair met while studying at International Christian University five years ago and spent a year dating long-distance while Princess Mako studied in England and Komuro in America.
The two met during their freshman year and became close in 2012 when they took part in an orientation session for study overseas programs.
After receiving approval from the emperor, the princess has formally announced her engagement to a commoner, and, in doing so, has signaled the forfeiture of her royal status.
Komuro, dressed in a navy blue suit, expressed his feelings toward the princess, shared his experiences from his days with her, and said when he sees a lovely moon in the night sky, he instinctively calls for Mako. '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'.More news: Merkel wants end to Turkey's European Union accession talks
The two 25-year-olds have been engaged since 2013, though the public didn't know about it until this year.
"First I was attracted by his bright smiles like the sun", Mako told a press conference announcing their engagement, as our hearts all exploded and we went "aaaaah" in unison.
In the televised conference, Kei Komuro described the princess as someone who quietly watched over him "like the moon". The formal announcement, that stunned all, was released by Japan's Imperial Household Agency on Sunday. Kei reportedly proposed to Mako back in 2013, but the princess's grandfather, Emperor Akihito, did not officially approve the engagement until September 3. But due to the unfortunate torrential rain that flooded northern Kyushu that month, the royal family chose to postpone the announcement.
Like all female imperial family members, Mako, who is Emperor Akihito's eldest granddaughter, forfeits her status upon marriage to a commoner under a controversial tradition.More news: United Kingdom minister: European Union commission criticism of Brexit talks was 'silly'
The 83-year-old emperor has expressed a willingness to abdicate the Chrysanthem throne and could reportedly do so in December 2018.
The happy news is not necessarily good news for the future of a royal family facing concerns about a declining population to keep their 2,000-year-old bloodline going.
The couple maintained a long-distance relationship as Mako studied in Britain and Komuro in the USA for one year.
The princess works as a researcher at a Tokyo museum, while Komuro, a resident of Yokohama city, south of the capital, is a legal assistant and undertaking a Master's degree in business law.More news: Wenger: Lemar Rejected Arsenal, But We Will Try Again
Prince Hisahito is now third in line to the throne after his uncle, Crown Prince Naruhito, and his father Prince Akishino.