One day, Menou, an Executioner whose calling is to kill The Lost Ones, encounters a young Japanese girl named Akari. Like any other job, she goes in for the kill, but due to a certain ability Akari possesses, she’s unable to carry out her mission. In order to execute Akari, Menou makes her way to the cathedral in Garum, where a ceremonial altar exists that makes it possible for any off-worlder to be killed. Akari tags along with Menou on her journey, unaware that she is marching to her own death. However, as Menou watches the sheer joy Akari is having as they travel together, something inside her begins to change.

This is a story of a girl’s journey to kill a girl.