She is a former member of the Japanese idol girl group AKB48 and the founder of the fashion label Haluhiroine, which is distributed through Earth Music & Ecology.
[2] On July 20, Kojima was announced to be in a new sub-unit, Tentoumu Chu!, consisting of trainee members from AKB48 and its sister groups, together with Nana Okada, Miki Nishino, Ryoha Kitagawa, Nagisa Shibuya, Meru Tashima and Mio Tomonaga.
On April 6, 2017, Kojima transferred talent agencies from AKS, which managed AKB48 and most of its members, to Sun Music Production.
On January 12, 2019, Kojima announced her graduation from AKB48 during a Team K concert at Tokyo Dome City Hall.
On April 27, her graduation ceremony was held during the AKB48 Group Spring LIVE Festival in Yokohama Stadium.