Nensu stood in front of Midoriya, ready to go toe-to-toe with the presumeed-villain before he might do anything that could jeopardize the lives of many. Whatever this individual’s intentions were, she honestly didn’t want to find out, but rather tell him to leave, or stall for the Pros to sort out the situation. Maybe just long enough before he could ever use his quirk, if he had one. The only option she could think of, would be to stall. 
She stopped charging her right side, before any frost could form upon her being. The object he just revealed didn’t go unnoticed. “Who are you?”, Nensu spoke to the mystery character. His eyes were the first thing that made her remember...the villain back at the USJ who used a rather painful quirk upon her! She didn’t want to ask who he was again.