First Mission
Aria follows Kinji to the arcade where he manages to win some plush dolls for her. The next day, Kinji and Aria learn that a schoolbus has been hijacked by the fabled Butei-killer and fitted with a bomb that will explode if it slows down with an armed convertible preventing the passengers from interfering. As the busdriver gets injured when an attempt to stop the convertible is foiled by heat-detection, Aria and Kinji arrive on the scene, taking out the convertible. With the bus slowly running out of gas, Aria finds the bomb on the underside of the bus whilst Kinji finds and destroys the communications sensor. The bomb is disarmed by the sniper ace, Reki, but Aria is injured by another armed vehicle whilst trying to protect Kinji. As she is treated in hospital, she feels disappointed that Kinji didn't meet her expectations.
Aired 29/04/2011EP 3 - First Mission

Aria the Scarlet Ammo
Aria is a volatile girl who’s top dog in assault at a school for young mercenaries. When she discovers her classmate Kinji’s an ace, she strong-arms him into being her partner, but she isn’t the only femme fatale who wants a taste of his combat skills. His secret? He’s only a hotshot when he’s turned on! Aria gets Kinji for one mission, but he’ll end up with more than one finger on his trigger!
(Source: Crunchyroll)