The Scissor Blades were a weapon created by scientist Isshin Matoi as a way to combat the alien life forms known as Life Fibers and stop them from exterminating all life on Earth. This plan of his attracted the attention of a human-like Life Fiber creature named Nui. Nui steals one half of the Scissor Blade and leaves Isshin to die after defeating him. Giving the other half of the blade to his child right before his death, Isshin’s daughter Ryuko makes it her mission to use the sword to get revenge on her father’s killer and complete his ultimate weapon by taking back the other half from Nui.