Very little is known about Kosaburo's early life. At one point in time, he was training to become a Rocket member at the same time as Musashi, Kojiro, and Yamato. Yamato and Kosaburo were assigned together and now work as a team, capturing Pokémon for Team Rocket. There is a running gag, in which other characters usually call him by an incorrect name.

Strangely, Kosaburo was not seen with Pokémon in his possession until his third appearance; before that time, Yamato had always been the one to battle with her Pokémon. Kosaburo, however, has other skills typical of Rockets, including disguise and some physical prowess. He was able to pick up and throw Musashi into a wall.