In 2002, Tsugunaga auditioned for Hello! Project Kids with the song "Koi wo Shicchaimashita!" by Tanpopo. Her audition tape was aired on Morning Musume's variety show Hello! Morning. She was placed in the group with 14 other girls. In the same year, she starred in the movie Koinu Dan no Monogatari as the main character, Mao Morishita.
