"Fox Possession is an Otherworld Inspector"

In the empire that conquered the continent, there was a legend passed down among the nobility for the past 200 years about a person claiming to be an "Imperial Inspector." The true identity of the inspector, feared for ruthlessly executing nobles who oppose the empire, was a man and woman from another world who were transported from Japan 200 years ago. A man who became immortal after being possessed by a fox spirit and had become more than half demon, and a fox spirit woman who followed him to this other world, travel through the empire together, devouring humans today as well for the sake of their own purposes.