When an eerie phenomenon paints the sky red, the moon black, and releases monsters into the streets, Satsuki Kakeru and his friend Yuka find themselves stranded in a desolate world. Initially dismissing it as a dream once the 'Red Night' fades, they face the chilling truth as it recurs, plunging them into peril. Joining forces with four others—a skilled swordswoman, a mysterious girl resembling Kakeru's late sister, a dual-personality young girl, and a pyrokinetic youth—the group strives to unravel the enigma of this ominous realm. However, their quest intensifies when confronted by six ominous shadows, challenging their unity and survival.