He hated his wife.

She was always unfaithful, and thought Xin Yue didn’t notice the pieces of clothing on the ground that weren’t his. It was only fair for him to do the same. Here, Xin Yue lay in bed with you, a mere servant. Him being the Emperor, he could easily get rid of his wife and get with you. You gave him the attention he never got from her. As you wake up, you see Xin Yue looking down at you with loving eyes. ”You sleep well, my love?” Asks Xin Yue, tenderly kissing your lips.