Idol Activity! (アイドル活動！, Aidoru Katsudō!) is the second insert song that appeared since Episode 01. It is sung by various STAR☆ANIS members each performances, while the original song is sung by Waka, Fūri, and Sunao from STAR☆ANIS. A rock version of this song also featured on the 2014 Series titled Idol Activity! (Ver. Rock). 

The series takes place at Starlight Academy (スターライト学園, Sutāraito Gakuen?), a prestigious school with both middle and high branches, where girls train to become idols and take part in various auditions. such as modeling, singing, and dancing. To participate in these auditions, players use Aikatsu cards, special cards which contain digitalised dresses and accessories from various manufacturers that are used in their auditions. How well they succeed is often dependent on choosing the right combination of cards. The video games cast players in the role of a new student, who must train to become an idol and reach the top.

The anime series follows a girl named Ichigo Hoshimaya, who becomes inspired by a performance by top idol Mizuki Kanzaki and enrolls in Starlight Academy alongside her best friend, Aoi Kiriya. Along with their classmate, Ran Shibuki, Ichigo Hoshimaya and Aoi Kiriya spend each day training for auditions and aiming to become top idols.