Since they've been asleep for many and many years, a zombie girl kisses another zombie girl to transfer information about the current state of the world (don't ask why, this is the worst anime I've seen so far, zombie can do that too in this show don't ask)
https://www.deviantart.com/noogm/art/Aru-Zombie-Shojo-no-Sainan-Transfer-Kiss-935310695