More than 500 years ago, a man and his wife stood up against the vicious Demon King and challenged the immortal evil. They lost their fight, and he lost the love of his life and was rendered immortal. Now, Bryce Boltzmann works for the National Anti-Demon Agency (NADA), which operates under the guise of The Office of the Assistant Secretary for Health (ASH). Arcadia, a young university graduate, has been hired to work for the ASH — or so she thinks. Now, Bryce and Arcadia must work together to extinguish demonic forces in the modern-day world before it's too late.