Kojirou is the male member of Team Rocket, the evil trio that follows Satoshi around to steal his Pokemon.

Several times he's shown to have more of a conscience and the desire to be a good guy: in We're No Angels he seriously wanted the team to remain in a village where they were thought to be heroes. Contrary to Musashi, Kojirou is known to occasionally show morals, integrity and compassion and is shown to be quite kind to his Pokémon. Kojirou has also appeared to be more tactical in battles than his teammate Musashi.

Kojirou has a beloved bottle cap collection and had extremely wealthy parents, who are portrayed in the English dub as Southern aristocrats (despite this, he has no Southern accent). He lived a very spoiled and sheltered life, knowing very little about the world outside his home, but also suffered heavy restrictions and rules. He grew up disliking carnivals due to being driven past them unable to attend, and was left distraught when he was unable to get a Chimecho (a Pokemon he calls his "first love") as a result.

He finally ran away from home after his parents tried to marry him off to a girl named Rumiko, ironically almost identical in appearance to Musashi. His dislike of the many upper-class rules led him to believe that living a life struggling on the streets was better than a life where everything was given, which eventually led him to joining Team Rocket.

Although the team often appears in disguise, a common source of fan humor is Kojirou's habit of cross dressing or wearing women's clothes (to contrast with Musashi), makeup, and a history with violent, domineering women. It was this that led to the initial banning (the episode has aired after being severely edited) of the episode "Beauty and the Beach," that had Kojirou wearing fake breasts in order to win a bikini competition. In the original Japanese, Kojiro's effeminate tendencies are played up as a contrast to his smooth, baritone voice; while the English dub originally took this tack, Kojirou's voice has become progressively high-pitched and clownish as time has gone on.

The episode "Holy Matrimony" in which Kojirou returns home has a scene in which he goes to a cellar, only to be met by Rumiko dressed as a dominatrix, much to Kojirou's terror. The cellar is equipped as a full S&M dungeon which Meowth refers to as "weird gym equipment" in the dub.

The episode "That's Just Swellow" revealed that, at some point during his childhood, he was trained to be a Pokeringer champion by a former master, and is still extremely competent at it (reaching the final round in that episode before losing to Satoshi). He also has won a Pokemon Orienteering competition with his Mime Jr.

Kojirou carries a rose wherever he goes, and is occasionally shown holding it when Team Rocket recites the motto, but usually only when they are introduced to somebody new.