Izuku is a very timid, reserved, and polite boy, frequently overreacting to abnormal situations with exaggerated expressions. Due to yeаrs of being looked down on by Katsuki for lacking a Quirk, he is initially portrayed as insecure, tearful, vulnerable, and non-expressive. These traits are especially present around Katsuki, who also constantly harangued him for his aspirations to become a hero. He is not quirkless, he has One for All inherited to him by All Might. (But it’s a secret)