Not much is known about Katsuo's past, but he himself seems to know a lot about his boss Jirochou and his past with Otose. It is therefore believed that he was recruited early on to Jirochou's gang and became the junior leader at some point.
He has brown hair, black eyes and a distinctive facial scar going down from his forehead, between his eyes to his left cheek. He is very self-conscious about his hair and always divides it 7 to 3. He thinks his hair is look like Joe Odagiri and that fashion always come back in cycle.
Katsuo seems to be the standard yakuza-type who exploits and threatens people for money. He does, however, show another side to him when it comes to his dog, Meru-chan, which he shows great affection towards. He believes that 7 to 3 is the Golden Ratio that forms the basis for the entire universe and that everything will work out if it's divided by 7 to 3. Despite being a yakuza thug, he respects those who have guts, particularly Kyoshirou and Sadaharu.
Katsuo has been featured in various mini-arcs and appeared very early on in Gintama, when he and the Dobunezumi Group started trouble at the Male Host club because they wanted Honjou Kyoushirou to hand over the club to them so they could make money out of it. However, with the interception of the Yorozuya, their plan foiled eventually. Knowing he cannot beat the Yorozuya, Katsuo decided to give up.
His most notable appearance was in the 4 Devas arc, where he englightened Gintoki about Jirochou and Otose's past. As a junior boss under Jirochou, he first fought beside Chin Pirako against various inhabitants of Kabuki-chou, but was soon impaled by Pirako. Believed to be dead, he was being saved by Gintoki and was hospitalized. He appeared again as a guard of Otose later and was one of the first to realize that the Shinra along with Kujaku Hime Kada was the real enemy. After the events of the arc, he resumed his duty in the Dobunezumi group. With Jirochou and Pirako departure, he became one of the "new" Devas in Kabukicho.
Katsuo reappears and is shown defending Edo along with the rest of the cast.
- His name is based on Kurokoma Katsuzo (黒駒勝蔵).
- Sorachi Hideaki. Gintama. Shueisha, Vol. 35, Lesson 301, p. 15.
- Sorachi Hideaki. Gintama. VIZ media, Vol. 13, Lesson 105, p. 9.
- Sorachi Hideaki. Gintama. VIZ media, Vol. 13, Lesson 105, p. 11.
- Sorachi Hideaki. Gintama. Shueisha, Vol. 35, Lesson 309, p. 16.