Lucifer didn't doubt that if he ever had the chance to meet Castle, he would like the guy. Kate had made that clear, and everything she said helped confirm that.
Dropping down to the floor next to her, he said, "Well stop for a moment. Honesty is underrated. And I'm not Castle, nor would I expect you to feel anywhere near as comfortable with me as you would with him, I am your friend. And you're clearly missing him, so tell me more about him."