A spin-off manga titled Aria the Scarlet Ammo AA by Shogako Tachibana was serialized in Square Enix's Young Gangan magazine from November 2010 to May 2018, with an anime adaptation by Doga Kobo airing between October and December 2015.

The setting of the story features Butei (武偵, "war scout"), short for buso tantei (武装探偵, "armed detective"), a national qualification established to counter worsening crime conditions around the world.

Shortly after Kinji decides to quit the Academy for personal reasons, he is attacked by the Butei Killer, a criminal notorious for eliminating Butei—a case of the hunters becoming the hunted.

Aria the Scarlet Ammo is a light novel series written by Chūgaku Akamatsu, with illustrations by Kobuichi.

A manga adaptation, illustrated by Yoshino Koyoka, began serialization in the November 2009 issue of Media Factory's Monthly Comic Alive sold on September 26, 2009.

A 12-episode anime television series adaptation,[77] directed by Takashi Watanabe and produced by J.C.Staff, aired in Japan between April 15 and July 1, 2011.

[79] An anime adaptation of Aria the Scarlet Ammo AA, a spin-off manga series written by Shogako Tachibana and produced by Doga Kobo aired in Japan between October 6 and December 22, 2015.