In future Tokyo, a young woman in the privatized police force tracks down her father's killer while battling against mutant rebels known as engineers.

Set in a future-world vision of Tokyo where the police have been privatized and bitter self-mutilation is so casual that advertising is often specially geared to the "cutter" demographic, this is the story of samurai-sword-wielding Ruka and her mission to avenge her father's assassination. Ruka is a cop from a squad whose mission is to destroy homicidal mutant humans known as "engineers" possessing the ability to transform any injury to a weapon in and of itself.—Anonymous

In futuristic Tokyo , the police have become privatized and are in an ongoing battle with a race of super criminals known as Engineers , which have the ability to turn any injured body part into a weapon . The no.1 engineer hunter , a samurai wielding assassin named Ruka , hunts them to uncover her father's killer.