The energy sensed from Remus was building up, and Leo could feel it. He knew that Remus still had a lot left in the tank even after fighting and using so many abilities. Although Leo and Silver weren't hurt, it was hard to imagine them winning without getting seriously hurt in the process or losing something of importance.
However, Leo was clear what their goal was, it was to bring back the vampire knight in one piece, not to defeat Remus. If he was on his own, then maybe he would use everything he had in his arsenal to try to defeat the person in front of him, only risking his own life. He had even considered that for a second, but the problem was what that would cost?
