The demon king indicated that his four heirs could become the next demon king by finding the last descendant of a demon slayer and marrying her. The four heirs arrived at a human school with their own motives. Meanwhile, in an attempt to retrieve her mother's bracelet, the woman offended one of the demon heirs and found herself burdened with a massive debt. Helplessly, she was forced to become their maid, but she accidentally discovered a secret about the family: they were not all human! Thus began a series of adventures.
