"Death Zone" starts off with Mikami in their usual modes.
But the advent of a goddess sends the two sweepers back to medieval Japan. There they meet their reincarnation-ancestors, with Yokoshima's being an exorcist while Mikami's is a demon, and of course both of the ancestors look roughly like their descendants. Though the demoness Mephisto is initially subservient to exorcist Takashima, she can't keep the dominant Mikami nature from surfacing.
In Mephisto's case, her animus proceeds from a sort of feminine modesty. To what extent such modesty influences Mikami remains an unanswered question.