Kasumi Toyama and the members of Poppin'Party—their high school band—are now second-year students, but with the new school year comes their latest set of challenges: student council duties, cram school, and part-time jobs, among other things. Furthermore, they are now separated into different classes, and as a result, their free time together is shortened. Looking back, their joyful times together seem like nothing more than an unachievable fantasy when their members are too occupied to even gather in Arisa Ichigaya's basement for practice sessions. As the band ponders over the situation, an unfamiliar girl suddenly emerges, unknowingly pulling them into the spotlight once more.

In this rising era of girl bands, Afterglow, Pastel*Palettes, Roselia, and Hello, Happy World! begin to make their appearance as well. Each band, comprised of musicians with their unique personalities, illuminates the stage with its performances. As Poppin'Party returns to the music scene and encounters new friends, the sparkling, heart-pounding music starts to play once again!

BanG Dream! 2nd Season is a part of the "BanG Dream!" multimedia franchise, which was developed by Bushiroad in January 2015.

The franchise also released a mobile rhythm game, titled BanG Dream! Girls Band Party! for iOS and Android, which was developed by CraftEgg and published by Bushiroad. The Japanese version was released in March 2017, and the English version in April 2018. As of July 30, 2018, the game has surpassed 10 million downloads worldwide.