Personality
Koby was initially introduced as a cowardly Chore Boy on Alvida's ship. Out of fear of being hit by her Iron Mace, he would always reply, "You are, Miss Alvida," whenever she asked who was the loveliest on the sea. With Luffy's help, he found the courage to leave Alvida and pursue his dream of becoming a Marine.
The first sign of his transformation occurred when he and Luffy arrived at Captain Morgan's base. Despite Helmeppo holding a gun to his head, Koby gathered his courage and told Luffy not to worry about him. After their mini-arc series, Koby and Helmeppo became good friends.
Koby deeply values his friendship with Luffy, as shown when he asks if they're still friends even after a brief fight.
Abilities and Powers
In his first appearance, Koby lacked any fighting skills. According to Alvida, the only reason she kept him was because he was good at Navigation. During his mini-arc, he trained alongside Helmeppo and Vice-Admiral Monkey D. Garp. Since then, he has become strong enough to use Rokushiki, or at least Soru. He also has some knowledge of swordsmanship, as seen when practicing with Helmeppo and Garp's attendant.
Current Events
Koby appears at Water 7 alongside Helmeppo after Garp visits Luffy. He tells Luffy and Zoro about "The New World" and says that the next time they meet will be in the New World, where he will be an Admiral and will have to fight and capture Luffy. Luffy responds that he looks forward to their fight.
Koby sees Luffy one more time as he leaves Water 7 during Garp's attack.
Koby later reappears in the Marineford Arc, participating in the war alongside the Marines. After pleading for the war to end, he is attacked by Admiral Akainu but faints before being saved by Shanks.
His whereabouts post-timeskip are unknown.
