In a world where humanity is extinct and Earth is in a post apocalyptic state, worker drones struggle and toil to survive and defeat rogue robots called Murder Drones.
The series focuses on Charlie, the princess of Hell, and her quest to open a hotel for rehabilitating demons. Hell suffers from overpopulation and Heaven solves the problem by routinely exterminating demons yearly. Charlie, who has grown up in Hell, wants to find an alternate solution to the mass slaughter. She opens the Happy Hotel which aims at teaching demons and sinners to become better people. There is substantial resistance, though, and Charlie and her friends must work together to keep the hotel running.