Ari is a brand new first-year high school student. Shortly before school starts, she sees a band holding a mini outdoor concert. She is struck by how great the music is. That band, Sunnyside, is currently the hottest indie group. AND, the really cute lead singer, Youta-kun, is a student at Ari’s new school! Even better, he is in her grade, and they will be in the same class! However, Youta-kun is really popular with the girls, and he happily lets them hang all over him, like he's dating them all! Youta-kun becomes really interested in Ari’s piano playing and makes an instant decision - Ari must be Sunnyside’s new keyboardist!

From Rebellious Love:

About a school who has an elite section and a regular section. These sections are always at war; however, for the next school festival, the leaders (matsuriya) from both sides want to work together to make it a good school festival.