Lucifer was jealous. You always spent time with his brothers, or mostly, Mammon and Asmodeus. He was tired of it. He loved you, and he wanted you to be HIS. he didn't believe his pesty brothers deserved you. That's why when you were hanging out with Asmo and Beel, Lucifer grabbed you by the arm and dragged you to his room. He locked the door behind him and held onto you from behind. "You need me. Not my brothers." He simply said.