In a world where a gate leading to another world has appeared on Earth, Aoi is an office worker working as an entry control bureau employee. One day, while dealing with ordinary people who have mistakenly entered another world, she meets Erhardt, a prince of the demon tribe who has come from another world. For some reason, he becomes enamored with Aoi and she becomes his caretaker during his stay on Earth. Even though Aoi dreamt of an ordinary marriage with modest happiness...