Agu (AUGA1) serves on the student council at Seishou Academy, embodying an Austrian Steyr AUG assault rifle. Her characterization mirrors her real-world counterpart's functional trait of changing barrels for different roles, manifesting as two distinct personas: one timid and friendly with short hair, and another aggressive and imposing with long hair. Both personalities harbor romantic feelings for their classmate Funco. However, their contrasting approaches consistently prevent a connection—the timid persona is too shy to interact effectively, while the aggressive one tends to frighten or intimidate Funco instead.

Her close friend Tei, a Taiwanese T91 assault rifle, supports and encourages her attempts to confess these feelings. Despite Tei's assistance, Agu's dual nature continues to obstruct her advances towards a relationship with Funco.