Aqours is faced with a challenge after Uranohoshi Girls' High School ceases operations, causing Dia Kurosawa, Kanan Matsuura, and Mari Ohara to depart and leaving only first and second-year members. The group embarks on a search for a training ground, only to discover that their new school is unoccupied, as incoming students are sent to a different campus due to club responsibilities. Aqours adapts to their new situation but their plans are derailed when their third-year peers go missing during their graduation trip. Love Live! Sunshine!! The School Idol Movie: Over the Rainbow chronicles the remaining Aqours members' quest to locate their missing mentors and revamp the school in the process.