Just as nervous as Sophis was, the Empress was also but the difference between their nervousness was in their motive. The other one wanted the princess safe while the other one was nervous that her husband might fail to kill the princess. Seeing the princess repeatedly pierce her father without an ounce of pity, the Empress could see her dream of becoming the world's most indestructible being crumbing with each cut.
The Emperor decided to distract the princess so that his men would be able to carry out his assignment. With the way, the princess has pierced him so many times he knows that he needs their help to kill the princess with just one strike.
