He blocks it, but now he's got to deal with Darcy using her strength to keep his sword where it is with her own, essentially trying to pin it to his chest.

"You know if you use this on anyone who isn't asking for it, I'm going to kick your ass right. Also next lesson, a sword is a tool to keep your opponent away from you. Otherwise they do this-"

And she's going to try and headbutt him.