Aria the Scarlet Ammo summary: At Tokyo Butei High School, teens undergo rigorous training to become combat detectives, known as "Butei". Among the students is Touyama Kinji, an unremarkable young man with a unique ability to enter "Hysteria Mode" uncontrollably when near girls. During his Hysteria Mode, Kinji becomes an unstoppable force, fixated on protecting women, although he keeps this ability hidden. When a Butei killer targets Kinji and rigs his bicycle to explode, he is saved by transfer student Aria H. Kanzaki, an expert in assault. However, Aria discovers Kinji's Hysteria Mode and becomes fascinated by it, refusing to leave him alone.