Johnny's partner & fellow pirate bounty hunter. Though he wields a sword, he rarely gets to show his skill with it due to the level of the pirates he encounters after meeting Luffy. He and Johnny first meet Luffy & co. just after the "Black cat pirates" arc, when the tiny island he and Johnny are on is blasted by the Going merry while the crew is testing their new cannons. After they're both brought on board, Yosaku's bout of scurvy is cured, and they stay on the Going Merry for a while (since their boat was destroyed in the cannon blast). They tag along with the Straw Hats throughout the "Don Krieg" & "Arlong Park" arcs, after which they decide to remain behind at Cocoyashi village to help out the villagers.

Both Yosaku and Johnny seem to know Zoro from several years before he joined the Straw Hats. In the anime, how they met Zoro is shown in a dream Zoro has.