
I think Remi didn’t love the demon king…at first. No matter what, Emi will take priority, but in the second to last chapter she says that he’ll make her happy and that she’s sure she can come to love him, since he loves Emi’s Remilia. Since we never see another shot in the future it’s kind of hard to say she never loved him, but for sure it’d be love in her own way. I don’t think she’ll love him in the “wow my hearts beating super fast and I can’t speak” way but more like “if anyone touches you or does anything to you, their very souls cannot be saved from my wrath. Death would be a mercy for the things I will do are unspeakable.” Kind of way.

I agree, Remi sees the demon lord as the same level as the other people she needed to plot her plans. However as the story progresses, she had accepted the demon king’s proposal, even though her love is not the same as his(Demon king’s love is pure while her is tainted with ulterior motives) she then genuinely promised happiness for him. This suggests that the demon king have a special place in Remi’s heart though it’s not the same level for Emi, we can’t deny the fact that Remi was deeply touched by the Demon king’s words which would sound so impossible if its not from Emi. The demon king have truly become someone who stands out from the people Remi had used. It may not be pure love but hey at least there’s something.
Remi doesn’t love the demon king, but she love the part when he loves the Emi version. Since Remi technically wants to be a family with Emi, then creating a child would be the home for Emi’s soul. The demon king was just a the perfect candidate for it. Remi is just amazingly disturbing, they well portrayed a pure villain that would give the whole world to their loved ones, without straying away from their real nature up until the very end.