He is known as the "Dangerous Lion of Shinshinkai" (神心会のデンジャラス・ライオン, Shinshinkai No Denjarasu Raion).
A top student of Doppo orochi, who left the dojo after having enough of Doppo's "weak" training regime and trained around the world. He returns to Japan after finding out about the Underground tournaments. Katou's attitude is best described as arrogant, but usually being the butt of a joke; especially around Doppo, Katsumi, Tokugawa, and Baki. However, it is shown that he truly admires and cares for Doppo.
Katou is a man of average height with slicked back black hair.
Katou is a strong fighter and one of the greatest Shinshinkai student. He loves to using a lots of dirty moves during a fight, such as eye poke and ball kicking. In the second series, he uses a fishrod's rope and rubber tube as a weapon. He used it to cut Dorian's ear in a surprise attack. Even that he was brutally beaten by Dorian and had his face scarred with a broken bottle. He has high durability: despite of being almost beaten to death and had his neck cut with a super-thin metal wire, he survived.
In the volume 21 of the first series, his fighting style has been defined as the "reckless karate art" (無頼派空手, Buraiha Karate). It was a reference to a Japanese group of writers – the Buraiha, known also as the Decadent School.