One punch man then is very rude when he kills the opponent mid-speech?

This assumes A can only lie. But I guess that is the riddl.

How though?

A truth B lies

Ask A: answer is No (truth)

Ask B: answers is No (lies)

Well you should assume that both guards follow the rules all time. Meaning that the initial setup of the rules cannot be trusted, because who knows if the talking Guard is lieing or not. If one does tell nothing but the truth this must be the one explaining the rules.

However if I remember correctly it was setup that one will answer the truth while the other one will deceive me. Meaning he might tell the truth if it confused me.

So no question might work.