After the death of his father and older brother, young Kazuki Kayne wastes no time in shouldering the burden of responsibilities thrusted upon him to end his family's impoverished lives and restore their happiness. All he wishes is to live a quiet and peaceful life with them by his side. However, they live in a country that is terrorised with blood thirsty, man eating creatures called Xenos, who only prowl the land at night. An ill-fated doom falls upon the Kayne family as their home is attacked by a mysterious Xeno, horrifically murdering Kazuki's mother and two younger siblings, leaving only him and his blind, twin sister Kaya as the only survivors. Fueled by malice and hatred, the siblings join a mysterious organisation known as the Xeno Hunters and swear vengeance upon their family's death. They will stop at nothing to hunt down their family's murderer and put an end to any Xeno who gets in their way.