Hibiki Mamiya is a sincere young man with a bright personality. He works as a car mechanic and lives with his girlfriend Kurumi Ogasawara. They have dated since they were high school students. Hibiki Mamiya makes a plan to propose to Kurumi Ogasawara. On the day he will propose to his girlfriend, he slides off a tunnel and becomes trapped. 4 days later, he is able to escape, but he faces a different world. There are no people outside, the traffic system is destroyed, and there are bloodstains on the streets. What happened to the world? Hibiki Mamiya tries to find Kurumi Ogasawara.