[2][3] Okada joined AKB48 in 2012, and since 2016 has been part of the group's main lineup, performing in all the title tracks of their singles, including twice as lead singer.

After joining Avex Asunaro, Okada has appeared in productions outside the group, such as the television series Stolen Love, High School Teacher (2021) and the stage musical adaptation of Magi: The Labyrinth of Magic (2022).

[11] In September, Okada was part of the cast for the AKB48 stage adaptation of the manga AKB49: Ren'ai Kinshi Jōrei, playing Haruko Mizuno.

For the group's 38th single "Kibouteki Refrain", Okada was not selected to sing the title track, but was assigned as one of the centers (lead performers) along with Nagisa Sakaguchi for one of the B-sides, "Ima, Happy".

[16][17] This was later elaborated in her solo documentary, aired in November on TBS as the fourth episode of the series AKB48 Inside Story,[e] titled "Nana Okada, 19 Years Old: The Price of a Dream".

[f][16][18] Since then, Okada has become part of AKB48's main lineup and performed in all the title tracks of their singles,[19] as well as her first solo song "Coin Toss" in the AKB48 album Thumbnail (2017).

[j][37][38] On March 14, the training and publishing company Benesse released an original promotional anime which featured Okada in her first voice acting role and "Shukkō" as its ending song.

[41] Okada stepped down as STU48 captain on January 18, 2020[42] and continued as a regular member until she officially left the group in March 2022, after her final single participation in "Hetaretachi yo" (2021).

1 Singing Ability Competition in December 2020[50] and joined the vocal group consisting of the event's top nine finalists, later named Nona Diamonds and represented by the agency Zest [ja].

[53][54] She reprised her role as Nero in the stage play Majimuri Gakuen: Loudness (2021),[55] where in contrast to previous installments of the Gakuen series, Nero calls for peace between the opposing factions in the end; idol journalist Hana Inukai connected this to AKB48's recent trend of reducing internal rivalry to present a united front.

[54] She took first place in the fourth Singing Ability Competition in January 2022[56] and was rewarded with her second solo song, "Kowasanakucha Ikenai Mono",[n] which was released as part of AKB48's 59th single "Motokaredesu" (2022).

The song is a rock ballad and the music video depicted her as a "fallen angel" singing on a building rooftop against a cityscape.

[57] In July 2021, Okada launched her individual YouTube channel and announced that she has joined the Avex Asunaro talent agency with the goal of expanding her solo activities.

[58] These include appearances in the television drama Stolen Love, High School Teacher (2021)[59][60] and a stage play adaptation of Magi (2022).

[67] On November 7, 2022, coinciding with her 25th birthday, Okada announced her first solo national tour, titled "Timeless Flag", which would take place from January to February 2023, with eight shows in seven prefectures.

[69] Following reports published by Shūkan Bunshun alleging that she and actor Hiroki Ino were in a relationship,[70] on November 23, 2022, Okada announced that she was leaving AKB48.

[71] Her farewell concert took place on April 1, 2023, at the Kanagawa Kenmin Hall,[72][73] followed by her final performance at the AKB48 Theater in Akihabara the next day.

[16] Her sister, Rina, occasionally accompanies her in live streaming sessions[88] and public appearances, notably at the 2016 AKB48 Janken Tournament where they cosplayed as characters from the anime series Re:Zero − Starting Life in Another World.