I, Lucifer, emperor of the demon race and ruler of the world, have been asleep for hundreds of years.  Now that I have been awakened, it is time to take back what was mine. But before that, I need to get back my lost core and the only being that can help me is a worthless human who is scared of anything and everything.  I should kill him when I'm done or my reputation will be stained for thousands of years to come.  What to expect; 1) Demons slaying 2) Human-demon wars 3) Mana 4) Academies 5) Holy relics 6) Slice of life 7) Powerful demons and humans