Akari Mamiya is in Year 1 at Tokyo Butei High School. Although she is currently in E Rank, her goal is to become a BUTEI like Aria Kanzaki, an Upperclassman in Year 2. In order to receive training from Aria, Akari submits a request to become Aria’s Amica.

Since there have been a series of attacks targeting BUTEI, Aria comes to stay with Akari and Nonoka for a while in case she’s being targeted by criminals who wish to retaliate against her. At the same time, Aria tries to see how Akari lives as well.

Kyochikutou’s sister, Suimitsutou, goes on a rampage while demanding to have her sister returned to her. Aria, Akari and the others work together to bring her down.