Two Puppet Parts

As the silver longsword shook slightly, Rhine suddenly blinked to the behind of the gate that hadn't been closed, leaving a slowly disappearing shadow behind. He said in both amusement and anger, "You met the monster that could pretend to be someone else, too?"

He sounded more or less relieved, as if he had confirmed that Lucien was authentic.

Lucien looked at him warily. After enhancing himself with Mechanized Mind and Mental Barrier again, he was rational enough to not directly attack Rhine. "Mr. Rhine, how can I confirm that you are authentic?"

You should at least give me an undeniable fact, or it will be better for the both of us if we go separate ways.