After losing his sister five years ago, Satsuki Kakeru led a vacant life, only able to return to his normal days with help from his childhood friend Minase Yuka and other friends at school. Suddenly one day, the sky turns red and the moon turns black. Everyone besides Kakeru and Yuka disappears and monsters start roaming the streets. All that they were able to do was just to run away and hide. After a while, the world returns to normal. But just when they thought everything was a dream, the Red Night occurs again. Kakeru and Yuka manage to find four more humans who are involved in this mysterious phenomenon: Kusakabe Misuzu, a red-haired onmyouji swordswoman, Tachibana Kukuri, a strange mute girl who looks like Kakeru's deceased sister, Hirohara Yukiko, a lively young girl who reverts to the personality of a cold killer when her glasses are removed, and Tajima Takahisa, a young pyrokineticist. They get together and try to survive, but six shadows suddenly appear in front of them...