Good on Kamui for refusing to exorcise one of the gal of the yuri couple. The whole premise seems rapey but it was never depicted like that. It is a battle between forces of life and death!
So Kamui had no reason to introduce a loving couple to Japenese style exorcism since they already partake in the wonders of life. Why (the girl) is torn watching the fight since they should be on the same side.