Kura had been frequently dispersing Damien's attacks.
Her unique talent to read another individual's energy and recreate its internal structure made her an obvious contender for the best in her class.
If attacks couldn't reach her, then wasn't it obvious that she won every battle she partook in?
Especially when people were conservative with information and unfriendly, it was easy for her to catch others by surprise and defeat them before they could get an idea of what she was actually doing.
Damien had a better connection to Nonexistence than most of those on the third island because of the events at Death's Hold. His innate perception ability was also marvelous. It was the talent that shined from when he was a teenager to now.
He saw exactly how she maneuvered her energy to mimic his. In his eyes, the interaction between the two invisible forces was clear as day.