She competed in the Miss Universe 2009 pageant on August 23, 2009, held in the Bahamas.

Miyasaka beat more than 3,000 applicants for the title of Miss Universe Japan.

[citation needed] Miyasaka's revealing national costume triggered backlash from Japanese critics, claiming the costume was "a national disgrace", "made fun of Japanese traditional clothing and culture", and was "a stupidly designed stupid costume for a stupid person to wear".

Originally, the skirt was longer, but Ligron decided to shorten it in a hasty decision taken before the press conference.

Nonetheless, Miyasaka wore a more conservative version of the design at the actual pageant.