For those who are worried about implications of grooming/pedophilia, i'd say that in this manga it isn't the case.
I believe the demon is mistaking her feelings of admiration as romantic, Evan meanwhile 100% treats them as if they were his child- he doesn't view them as a romantic interest or anything of the sorts. He notices the "flirting"(if you could call it that) she does, but he never takes them seriously. Although he does have a kind of charming or lowkey flirty personality, that's kinda just in his nature(as we've seen with how he acts with all the other characters).
That's just my two cents though, and I respect anybody who feels otherwise or uncomfortable with this manga.