Ancient style fairy/deep sadomasochism
She is a "witch" who is responsible for the blood feud of annihilating her clan, and he is the cold immortal who controls the way of heaven. The two fell in love and killed each other in their previous lives. In this life, they are misplaced and entangled, and in the end they can only exchange lives for lives.
She approached him step by step, intending to kill him for revenge, but she fell in love with him. She knows that all endings are dead ends, but she still flies into the flames.
He loved her so much that he was willing to destroy the world, but all he got in exchange was "I only treat you as my brother." In order to save her, he sacrificed millions of demons in the demon world, and eventually they all betrayed each other.
