natsuno-kanata - beyond the summer

A text adventure game depicting girls traveling the world to the end. You found an old computer which can connect to talk with strange garl you have never met. The girl's name is Natsuno. She said said to be traveling alone in a world collapsed by a pandemic. But in the world, you know, there is no pandemic or social collapse. Where is the world she is in and why are the calls connected each ot…