Mariko Shinoda

In October 2005, she auditioned for AKB48's first generation roster but failed the audition. Shortly after her audition, Shinoda began working AKB48's theater café – then known as Akihabara 48 – as a café attendant serving customers and handing out promotional flyers on the street. Shinoda became quite popular among patrons who soon learned of her failing her audition. To show their support, patrons began submitting her name on hand-written ballots for the weekly performer polls. Yasushi Akimoto, general producer of AKB48, took notice of her popularity and gave her a chance to join AKB48 on the condition that she learn the group's 12 songs and dances in four days. She became AKB48's first non-generation, or "1.5 generation", member with her debut on Team A on 22 January 2006. Her first single as part of the main group was on "Aitakatta".

On 30 March 2011, she began to host a show with her own name, Mariko-sama no Oriko-sama (麻里子様のおりこうさま!) on NHK. She has appeared individually in television commercials and was cited as the "queen of TV commercials" (CM joō) for 2012 for having more contracts (a total of 20) with companies to appear in their ads than any other female tarento (fellow AKB48 member Tomomi Itano was tied at 20).

In August 2012, AKB48 Theater's manager Tomonobu Togasaki announced sweeping team changes that placed Shinoda as the new captain of Team A.

In 2013, Shinoda launched her clothing brand "ricori" which featured clothing that she had designed and produced. She stated that starting her own line of clothing had been a dream of hers before joining AKB48. In July 2014, ricori ceased operation and closed down its stores. Shinoda stated she was working as an adviser for the label only until 2013.

Shinoda placed fifth overall in the 2013 AKB48 General Election. On 8 June, during the broadcast of the election results, Shinoda announced that she would be leaving the group. Her graduation ceremony was held on 21 July at the Fukuoka PayPay Dome, and her final performance at the AKB48 theater was on 22 July.

On 24 January 2016, Shinoda appeared as the lead actress in Korean rapper Zico's 'It Was Love' music video. He sang the song with Luna, the main vocalist of South Korean girl group f(x).