Katsuki is a very timid, helpful and polite boy, frequently overreacting to abnormal situations with exaggerated expressions. Due to being bullied since childhood for being born without a Quirk, he is initially portrayed as insecure, being more reserved and not self-expressive, especially in front of Izuku Midorya, who constantly subdued him for his aspirations to be a hero. However, after being accepted into U.A. High School, making new friends and facing Izuku during the Battle Trial Arc, he has gradually turned into a more confident and brave person, to the point of developing some leadership skills.