Kuroshitsuji, Mahoutsukai no Yome Recommendations
Both delve into the supernatural aspects of London, England. While one is about a boy who summons a demon in exchange for his soul, and the other is about a mage who buys a human to become his wife/apprentice; they both have very common themes. Sebastian and Elias seem to be very similar characters as neither is human and nor do either understand human emotions. They both try to help their human companions throughout their journeys to accomplish their goals.