This is a very simple story, we know each other, we still live in our own world, but everything has disappeared, just like the world is still turning without anyone, and people are calculated by age and lifespan. But even if we are gone and we can't go back to the past, those memories only belong to us, they are unique and cannot be copied.
This story may not be simple, because how can people be simple?
I leave you an umbrella to leave a trace in my memory.