Ghost Quartz  

, ゴースト・クォーツ

As a librarian and member of patrol duty, Ghost is responsible for managing long-term recovery facilities located on the fourth floor. Their preferred weapon is a sickle. Despite being quiet and calm, Ghost struggles with insecurity about themselves, believing that their fallen partner Lapis was superior. Due to having two personalities - Ghost and Cairngorm - they are vastly different from one another. Lapis Lazuli was once Ghost's teammate; after being taken by the Moon People, only their head remains. The library now falls under Ghost's care.