Kashiwagi took part in Morning Musume's Happy 8 Ki Audition (8th Generation Audition) in July 2006 and made it to the third round before being cut. She joined AKB48 after an audition in December 3, 2006 and debuted as a member of Team B at the "AKB48 1st Anniversary Live - Seizoroi da ze! AKB!" concert. Before her theater debut, as part of the "AKB48 Haru no Chotto Dake Zenkoku Tour - Madamada da ze 48" tour, she appeared in Yuko Oshima's position on March 17 at the Aichi Welfare Pension Hall and on March 18 at the Fukuoka International Conference Hall. Her first AKB48 theater performance as a Team B member was on April 4, 2007. On March 25, 2009, she joined Watanabe Productions. On April 25, 2009, she became a weathergirl on Tokyo Broadcasting System TV's "Hiruobi". She came 9th place in the member elections for the single "Iiwake Maybe" and was made captain of Team B on August 23, 2009. Her first solo photobook was released on September 20, 2009. During the AKB48 third general election, she was ranked third place by popular votes, after Oshima Yuko and Maeda Atsuko.