Coby first appeared as a timid cabin boy enslaved aboard the Alvida Pirates' ship. Monkey D. Luffy liberated him, inspiring Coby to pursue his dream of joining the Marines. Initially unskilled in combat, his sole noted ability was navigation. After enlisting, he underwent rigorous training under Vice Admiral Garp alongside Helmeppo. This transformed him from a fearful, physically weak boy into a confident Marine officer. Physically, he grew taller, developed a cross-shaped scar above his right eye, and adopted standard Marine attire while retaining his pink hair and habit of wearing glasses pushed up on his forehead. Coby's personality evolved from extreme cowardice to principled bravery. He remains compassionate and emotionally expressive, often moved to tears, but now acts decisively on moral conviction. A pivotal moment occurred during the Summit War of Marineford: using his Observation Haki to sense the deaths of countless soldiers, he confronted Admiral Akainu to halt the massacre, enabling Luffy's escape. This act demonstrated his commitment to justice over blind obedience. Post-timeskip, he achieved the rank of Captain and joined the covert Marine unit SWORD. His heroism during the Rocky Port Incident earned him widespread acclaim and a 500,000,000 berry bounty from the Cross Guild. His abilities expanded significantly under Garp's mentorship. He mastered Rokushiki techniques like Shave and Tempest Kick, and developed advanced Observation Haki capable of perceiving emotions and imminent deaths across vast distances. He demonstrated formidable combat prowess by shattering a gigantic metal disk with a single punch. Despite his growth, he maintains humility, rejecting the "hero" label and prioritizing others' safety. Relationships define Coby's arc. He shares a deep bond with Luffy, whom he considers a friend despite their opposing allegiances. His mentor Garp acknowledges his potential, leading a rescue mission when Blackbeard captured him. Helmeppo evolved from a spoiled rival into a loyal comrade who supports Coby unwaveringly. After escaping captivity with SWORD's help, Coby continues upholding his ideal of a "real Marine," balancing justice with empathy. Recent developments confirm his ongoing relevance, including involvement in high-stakes missions and his symbolic status as a beacon of reform within the Marines.