Natsuno, a girl who leaves her hometown of Tokyo and continues traveling alone to the north. She is alone. She left her high school classmate at Tokyo, and got separated from her parents at some station. After the train stopped working, she walked alone and continued her journey. She had'nt where to go and any purpose. The world has ended before half a year. An unprecedented pandemic has destroyed society in just a few moments. When infected, a person loses reason and becomes a monster cannot speak that attacks the person. Neither the causative virus nor the bacteria were finally revealed. People don't know anything. Still, what is in front of her is just reality, Even if she walks around the town, she don't meet anyone and have no choice but to continue her journey alone. You happened to talk to a girl traveling in such a world. It all started when you found an old computer, throught my grantmother's possessions after her death. Looking for memories with your grandmother, you opened the data on your computer. But what I heard from the computer was the voice of an unknown girl ── You dont know why but a call was connected to a girl who called herself Natsuno. Of course, there is no pandemic in the world you live in. High school students enjoy their summer vacation, they don't wander around an empty town. Still, it's true that Natsuno and the call are connected. Where is she? Why can the call be connected? There were so many things I didn't understand, She just "talk to me," she said. While meeting other girls who live in a world that has ended, You gradually approach the truth ──