Katsuki is a crude, arrogant, short-tempered, and aggressive person, especially at the beginning of the series. Katsuki tends to come off as unheroic; this problematic behavior going all the way back to his early childhood days. He has a soft spot for his classmates, but he would never admit it. He is known as Kacchan by his childhood playmate, Izuku, who he always calls by the nickname Deku. His best friends are Kirishima and Denki.