A single, shining moment of youth becomes the gateway to an endlessly expanding hell of slaughter. An ordinary high school boy, Jou Kosaka, encounters a beautiful girl, Nagisa Tamura, who appears before him and asks, “Will you protect me?” From that moment, his normal life is thrown into chaos and becomes anything but ordinary. A pleasure-driven killer with no motive known as the “Dimensional Rider” targets Nagisa. With her death, time begins to loop for the two of them. Can they escape this cycle of endless time and killing?