The nations recognized Rui even with his mask on. Martial Artists were distinct and Rui was very infamous at this stage. Every nation had had a hard time containing him in war. He was simply a menace and no individual Martial Artist lasted very long against him.
However, he by himself could not compensate for an entire army. The nations felt more confused than offended. What were they trying to do? Were they just sending a single Martial Apprentice to speculate the war and gather intelligence from a distance?
However, the Kandrian Empire did not need to engage in such tactics for surveillance. It was also quite clear that Rui wasn't primarily or even significantly a sensory-oriented Martial Apprentice. Thus, there was no way that Rui was being deployed due to a need for surveillance, there were many more fit Martial Apprentices that could be deployed for this particular role.
So why send their ace Martial Apprentice all alone in the middle of a war?
