What Should I Do If I Am a Genius in Cultivation and Adopted by the Demon Lord?

Thousands of years later. "May I ask you a question?" "You asked." "What would you do if your adoptive father who you grew up with was your family-killing enemy?" "What kind of idiotic question is this? How could you be left alive after destroying your family, waiting for your revenge?" The woman stood up and left, expressing her silence at the question. So she didn't hear the other girl murmuring in a low voice: "... Where are you idiot? I'm the one who was left behind."