Mei, the daughter of a family that exterminates vicious monsters, was raised in a cold environment, lacking the power to exorcise demons. Meanwhile, her arrogant younger brother violates a taboo and awakens Ryouga, the king of another world! Mei is left behind... Mei is in danger, but Ryouga is actually a gentle, intelligent, and handsome young man. He teaches her the value of the rare "healing power" she possesses, and invites her to "become my princess."