Although I usually avoid them like the plague - I need to know if there is an ML and who it will be now. I start to see weird things. Emiel has the typical traits of an ML (mysterious past, hidden scars, both physical and psychological, strong and powerful, always ready to throw his life away at the smallest things and of course there is that self-demeaning habit of his that seemingly only the MC can cure xD) the only thing that speaks against him is the slightly bigger age-gap and that he is no prince or of higher status... and look at all his screen time xD I think that would be a refreshing pair (she is probably living a very long time, given she is a Castillo, she wouldn’t be able to become happy with a normal mortal man anyways, so for people like her age-gaps are probably not a big thing (?) - since he is a master, his life might be prolonged as well).
Well, still, I don’t need the romance now - since she is still a child, but one day she will grow up into a beauty - if Emiel stays her guard he will have his hands full protecting her from the sidelines.