When Chinese Foreign Minister Wang Yi calmly but staunchly asserted Tuesday night that Japan-administered islands in the East China Sea belong to China, a slight smirk appeared on the face of his Japanese counterpart, Toshimitsu Motegi.

As the interpreter subsequently read Wang’s remarks aloud in Japanese, Motegi’s expression changed little but his darting eyes belied a certain unease. Some observers speculated that he had frozen, and the faint smile was simply a defense mechanism.

The contrast was sharp between Wang, who maintained a poker face throughout, and Motegi, who appeared to have been caught off guard by the Chinese envoy’s spontaneous assertion about the Senkaku Islands, which are known as the Diaoyu in Chinese.