Quartet refers to an actual fighting test between two four-person groups and is a requirement for all the Year 1 students at Butei High. Akari forms a group with Shino, Raika and Kirin and trains to defeat their opponent, Urara Takachiho’s team.

Aria is injured in a gun battle and taken to the hospital. Meanwhile, after Kyochikutou declares that no one will have to get hurt if Akari surrenders to her advances, Akari tries to send Nonoka to stay with their aunt in Nagano.