That's enough for him. Saitou lets her stop him but even as he's doing so he's turning to grab his sword from his right side with his left hand and he takes it to keep one fluid motion for him and slash out with the blade in a horizontal arc to strike at the woman who isn't hanging onto his arm, anymore. The girl that halted him is strategically protected just by the way he pivots his body Ending with her behind him.

It had been obvious, after all. Perhaps he's become too paranoid from Belin and is overestimating his remaining enemies and they capabilities to deceive. Enough of this, then. Choice made.