A small company dedicated to bringing happiness to the world receives a simple request to help a woman's unhappy son smile again, but the job turns out to be more complicated than it seems.
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.