Dog-Licking System: Demon Lord's Favorability Towards Me Is Full

On the night when my family was exterminated, I died tragically under the sword of the Demon Lord, but was forcibly resurrected by the "enemy favorability system". The system says: The higher the hatred value, the greater the gain from the strategy. So, I became the personal servant of the enemy who destroyed my family. When he let down his guard against me, it was also the beginning of my cultivation to crush him.