Some heavy spoilers ahead, don't read if you haven't seen episode.
Humans destroyed earth's nature in the past and later created place to live to the moon. Underground world where devices maintain normal living conditions.
Ura works in the bureau of record excavation and try restore old records. Before there were much more workers, but most of them didn't want to remember sad past anymore and quit. Ura is different, he is almost obsessed to search archives.
One day Ura find something strange, video where woman read old regular book and sing. He get sudden urge to go and see earth with own eyes from the surface of moon. Instead of rusted earth like it was in past, Ura sees blue as sign that planet have recovered from the influence of humans.
I am speechless. Awesome animation, very interesting story, good music. Even if it's scifi it feels so real. Watch this.