Bit late to the party, but I really love the detail of Kei no longer feeling love or hatred for humans, it's just indifference
Which was, obviously, stated in the previous episodes on the clock, the opposite of love isn't hatred, but indifference
From what I recall, the demons know that they do not feel empathy, and many other human emotions, and don't really care, but don't fully understand it either. Macht ended up getting interested in humans and their emotions, hence him choosing to interact with humans to learn more about them...