Hidan no Aria

is a Japanese light novel series written by Chūgaku Akamatsu with illustrations by Kobuichi. As of March 2011, 9 volumes have been published by Media Factory under their MF Bunko J label. A manga adaptation by Yoshino Koyoka started serialization in the seinen manga magazine Monthly Comic Alive on September 26, 2009. An anime adaptation has been announced, and was released on April 14, 2011. Twelve episodes were televised and a 13th episode was released as an OVA in December.

Plot
With crime rate on the rise, special students are chosen to enroll in Tokyo Butei High School, a school dedicated to train armed detectives called "Butei". Among these students is second-year student Kinji Touyama, who seeks a normal life. However, he is dragged into a more exciting school term when he meets a girl named Aria H. Kanzaki in a life-threatening situation.

Official

 * Official light novel series website
 * Aria the Scarlet Ammo FUNimation
 * TBS

Other Sources

 * Wikipedia
 * Anime News Network