Demon in Frieren World

You were reborn in world of Frieren - and you are a demon. Timing is in wery old times - Frieren is not even born yet. There are still many elf settlements- humans do not have big kinghdoms - only scattered settlements. There are thousand years before main story will start. And it is for you to prepare for what will be. There is a Demon King - but you do not bow to him, you are free demon now - and not even met any other demons yet. But... you already acknowledge how powerfull this race it. Your brain is supercomputer. Your control over mana is natural. With your mind of human from 21st century... how far you can go? What accomplish? All demons are evil to humans and other races - they do not even understand concept of what moral is. But you do. Is it weakness or power? Only time will show it.