Born in a clandestine government laboratory that cultivated esper (telepathic) abilities in humans, Shuuichi and his two sisters, Sumire and Katsumi, were compelled to endure a harsh existence as test subjects until they escaped. Years later, these siblings remain pursued by unknown organizations seeking Shuuichi's powers, as he is what they designate the "zero-sample" with the capacity to trigger "zero-shock."