Later, her parents changed their minds after attending a Nogizaka46 concert in Fukuoka and allowed Nagahama to participate in the new group.

With the support of the judges from the auditions, Nagahama officially joined Keyakizaka46 in November 2015 during the group's weekly variety show, Keyakitte, Kakenai?

[4][5] Nagahama made her musical debut with Keyakizaka46's first single, "Silent Majority", though only appearing on a B-side song, "Noriokureta Bus" (乗り遅れたバス).

[10] In December 2017, Kodansha announced that they will be publishing a photo-book featuring Nagahama photographed on the Gotō Islands, her hometown.

[13] Nagahama has appeared in all singles up until "Kuroi Hitsuji", and was also included in crossover groups such as Sakamichi AKB (with Nogizaka46 and AKB48) and IZ4648 (with Nogizaka46, AKB48, and Iz One).

[14][15][16] After the release of Kuroi Hitsuji in March 2019, Nagahama announced her resignation from the group, citing personal reasons.