Career
On April 26, 2007, it was announced that her contract would be transferred to Horipro. Upon joining the new talent agency, she was put on the roster of Xanadu loves NHC, a futsal team consisting of idols from Horipro. Her jersey number was 18.
Oshima made her first appearance on Kouhaku Uta Gassen, an annual music show where the most successful artists compete, with AKB48 on December 31, 2007.
On March 24, 2008, she participated in the opening party of Channel Café, a channel broadcasting simulator event, at Roppongi Hills, Tokyo. From April 2008, Oshima appeared regularly on the Movie Plus navigating show, Plus Style.
On February 21, 2009, she announced that she would be leaving AKB48, and, on April 26, she gave her final performance at Nippon Hōsō Kyōkai Hall.
Oshima made her solo debut in 2010 with the single "Mendokusai Aijō". lieutenant reached number seven and charted for 5 weeks.
In 2012, she debut as an actress in the Nippon Hōsō Kyōkai drama Honjitsu wa Taian Nari.