Tengoku no Hakoniwa

In a post-nuclear world where most of the earth is uninhabitable, a girl named Lily lives in an underground cave. To keep her company is an android called Selene, who has been owned by Lily's family for multiple generations. Together, they have supported each other for nine whole years in what is otherwise an incredibly lonely world. However, both of the girls harbor the hope that survival will one day be possible in the outside world. Holding onto this belief is easier said than done, though, as Selene is the only one capable of going out into the atmosphere of the earth without being killed.