Once the apocalypse starts Avianna is left alone to survive. Hardly being able to tell who is alien and who is human, she has to decide who she can trust and who she can not. (I'll write a better description soon.)
Everyone definitely wants to be able to time travel. The same goes for Arata Satou, a Class 10 student who attends a well-known school in Southeast Asia.
The story tells of Arata, who just wanted to go to the toilet but accidentally traveled back in time. Arata realizes he is at the same school, but it's three years earlier.
In a state of panic, Arata tries to find a way to return to the present while trying to understand the strange events that have happened to him...