Captain Kuro, also known as Kuro of a Hundred Plans, is the former captain of the Black Cat Pirates and serves as the primary antagonist of the Syrup Village Arc. Before the events of the story, Kuro grew weary of the constant pursuit by the Marines and the chaotic life of a pirate. To escape this existence, he orchestrated an elaborate scheme to fake his own death. He had a crew member disguised as him and allowed a Marine officer named Morgan to take credit for the capture, resulting in the execution of the impostor and the revocation of Kuro's bounty.

Following this, Kuro assumed the alias Klahadore and infiltrated Syrup Village, becoming the trusted butler and caretaker of a wealthy young orphan named Kaya. His plan was to spend three years earning her trust, after which he would have his former crew attack the village, force Kaya to write a will leaving her fortune to him, and then kill her and the rest of the villagers to eliminate all witnesses. He viewed this quiet, wealthy life as a far more desirable goal than the constant running and violence of piracy.

Kuro is an extremely intelligent man, noted to possess the second-highest IQ in the East Blue. He is a master strategist who takes immense pride in his plans, which he claims have never failed. This pride is a core part of his identity, giving him his epithet. However, this confidence borders on arrogance and leads him to underestimate opponents he deems inferior. While he desires a peaceful retirement, he is not a reformed man; deep down, he is cruel, bloodthirsty, and hypocritical. He despises pirates for what he calls their barbaric greed, yet his own scheme is built on murder and theft. He holds his subordinates in complete contempt, considering them disposable pawns to be sacrificed for his goals. This disregard for life extends to his own crew, as he planned to kill them all after they served their purpose to ensure his secret remained safe. His murderous nature is particularly triggered by the sight of a crescent moon, which drives him into a feral, uncontrollable rage.

In his role as Klahadore, Kuro is a skilled actor, presenting a facade of a gentle, loyal, and slightly snobbish servant who claims to despise pirates. He maintains this persona for three years, all the while secretly loathing Kaya and the villagers he must serve. When his plan is set in motion, he discards this mask to reveal his true, callous self.

Kuro's role in the story is as an early obstacle for Monkey D. Luffy and the Straw Hat Pirates, who befriend Kaya and Usopp, a young villager who idolizes pirates. The crew uncovers Kuro's plot and moves to stop him. His key relationships are defined by deception and utility. He views his first mate, Jango, as a useful tool for carrying out his orders but ultimately plans to discard him. He feels nothing but contempt for Kaya, seeing her only as a means to obtain wealth. His primary conflict is with Usopp, who sees through his lies and rallies the villagers to fight, and with Luffy, who ultimately challenges him directly.

Kuro possesses notable abilities that make him a formidable fighter. His primary weapons are a pair of gloves known as Cat Claws, which have long, sharp blades attached to each finger, allowing for slashing attacks. He is most famous for his incredible speed, which is a precursor to the superhuman Rokushiki technique known as Soru. His signature attack, the Shakushi or Pussyfoot Maneuver, allows him to move so fast that he becomes nearly invisible to the naked eye, slashing everything in a wide area indiscriminately, including his own allies. The main drawback of this technique is that he himself cannot see what he is attacking while moving at such speeds. His habit of pushing up his glasses with the palm of his hand, rather than his fingers, is a visual reminder that he is always ready to kill without damaging his blades.