"There are different ways to do things than that way." Talking about what Lucifer just pulled on him. There are other ways to work to the you are a blood sucking vampire revelation. Seimei just narrows his eyes at the last part. That's the part he heard clearly. Instead of acting on the anger, which he's trying to hide and he's partially failing, and trying to hurt the other in some way, Seimei just gets up and heads for the door without saying anything.