The story takes place the day before the proposal. A young man named Hibiki Mamiya is trapped in a tunnel slide accident. After escaping the tunnel, the world has changed dramatically. There are deserted streets, a large number of corpses, and "living dead" wandering on the streets. In this abnormal situation, Hibiki, who is left alone, desperately searches for his lover Raimi, but can't find him. Soon, Hibiki finds that this street has been blocked as a warning area, but there are also some survivors among them. Are they partners living together in this desperate situation?