Obviously that would work, but I don't (as far as I understood it) think that was the original question. Rather, the question was if there was a defence for that specific situation - where you are NOT standing far away, but rather very close.
I think ma-ai is the answer to an effective defense, because I think the attack had begun some time before the actual weapon was used. The attack did not begin when he slashed the victim, it began when he was talking, closing the distance, setting up his position, looking for a moment of inattention. To phrase the question, "what is the effective defense?", should allow that the defense can begin at the same time as the attack.