I've been reading manga for 8 years now and I came across a certain manga but I can barely remember certain details

its about a guy who raises a child that has a mark of a demon (its heart 😕 something like that... i think), meaning the demon has given the child a prolonged life and when that child grows to be a certain age he will reappear to claim his mark.. As the story progresses it turns out the man who raises the child is in fact the demon who gave her the mark.....(don't remember the rest) and they end up together

something along those lines 😕

sounds like Hanatsukihime maybe