Shoko Kamano, 28, who promoted tourism for Shonan beaches in Kanagawa Prefecture with Komuro in 2010, said she was "really surprised" to know he was marrying the princess but "truly happy" to hear the news.
The couple seems to have a loving relationship as they both revealed their feelings during the press conference.
Princess Mako's sacrifice for love has reignited a national debate in Japan about whether women should be allowed to retain Imperial status after marriage and rise to the throne.
The agency, which initially planned to disclose to the public the couple's informal engagement in autumn this year or later, moved up the schedule to July 8, following a flurry of media reports that preparations were under way for the engagement of Princess Mako and Komuro.
In a press conference on Sunday, she said she was first attracted to Kei Komuro's "smile like the sun".
Watch World Cup Qualifying match on TV, online
Substitute Welbeck made it three in added on time , on his return to worldwide football, as he beat Hogg to Kane's cross. The Three Lions face Malta tomorrow night as they continue their bid to reach Russian Federation .
'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 princess said that she will marry Kei Komuro, who was a classmate of hers at Tokyo's International Christian University.
Her engagement is set to be announced in the coming weeks. Princess Mako is the first of the Imperial House's four grandchildren to get engaged. According to the ceremonial rituals, "Komuro's messenger will visit the princess' Imperial residence with gifts to formally vow engagement", the Japanese website writes. In this ceremony, Komuro's messenger will announce the wedding date. "This is truly happy news that cheers up the citizens of Japan", Prime Minister Shinzo Abe said in a comment on the announcement of the princess's engagement to Kei Komuro. The wedding is likely to take place in fall next year.
In 2016, 83-year-old Emperor Akihito announced publicly that poor health following heart surgery and prostate cancer had made him unfit to properly fulfill his duties as emperor of the country.
The Princess graduated from university with a master's degree in art museum and gallery studies and now works as a researcher at a museum at the University of Tokyo. Since then she has attended official events as a member of the royal family, visiting victims of the 2011 Tohoku natural disaster and tsunami.