I don't think it's a demon, but witches.
I thought it was an entity that wants the plot always going the same way and repeating itself forever. But I'm not sure.
Well, yes and no. From what I've remembered, the "story" or world is being controlled by some entity, but I think there was a chapter where the ML called them "witches". These witches cursed the ML or something to continue to suffer over and over again. I don't know what happened nor what he did, but it seems like the ML is the only one before the FL appeared to seem to know what is going on. This is not spoiler by the way xd it's a theory.
is the demon hater being backed up by a demon right now ??