Kaga lifted his head to see what was going on. He saw that Dante was back and not very happy about Virgil being there. When it became apparent that Dante was going to kill Virgil, Kaga stood up and said sternly, "Dante, wait! I don't like the pathetic twerp either, but at least hear him out! He is your brother, after all."
As much as he hated Virgil, Kaga didn't want Dante to kill him. It was more for Dante's sake than for Virgil's that Kaga spoke up. He didn't want to see his friend, who he respected, murder someone in cold blood.