The protesters began their march from the central entrance to the Hibiya Park, holding placards calling for preventing the marriage of the princess, "prevent deception" and "protect the imperial family".
The couple officially registered their marriage earlier in the day and now plans to move to the United States, where Komuro works at a law company.
After the ceremony, the newlyweds delivered an address in the presence of journalists, who were only able to submit questions in advance. The ex-princess said she regrets having caused some people trouble in connection with her engagement and marriage that caused quite a buzz since the announcement. She also thanked those who had supported her despite a financial dispute involving Komuro's mother.