More than ten years ago, the "aberrant beings" suddenly appeared all over the world. With forms similar to creatures from various legends and mythologies, these "aberrant beings" led countries to gather their best specialists to confront them... People called them "exorcists." A young man named Tojuro, who works as an exorcist due to his family's circumstances, dreams of living an ordinary life. However, during one of his missions, he encounters Behemoth, a legendary sacred beast mentioned in ancient legends. But, despite being an "aberrant being," Behemoth does not have the appearance of a monstrous beast; instead, she takes the form of a beautiful woman.