[ Nezumi notices the change in expression. Part of surviving in knowing how to play with whatever actor you're staring across. He's not sure what about his words made Setsuna go to a dark place, but something did. ]

You already know it's a quote.

[ And he's not kind enough to allow the moment to pass. ]

If you don't like Chekhov, I can do others. Shakespear's more of a favorite, anyway.