Their captain, Kuro, had a 16 million bounty on his head at the time, so he was constantly hunted by the navy everywhere he went. He disliked this stress more and more every day, so he came up with a plan to lose his bounty and leave the pirate life behind. He captured a navy ship and killed the entire crew, leaving only the ship’s captain, Morgan, alive. The vice-president of the Black Cat pirate gang, a hypnotist named Jango, hypnotized the ship’s carpenter of his own crew to believe he was Kuro, and Morgan to believe he had captured Kuro single-handedly. Thus the ship’s carpenter of the Black Cat pirate gang was executed in place of Kuro, and his bounty cancelled. In the night and fog Kuro left the pirate ship, left the captaincy to Jango and moved to a small island called Syrop, only with the request to do him a favor there in three years.
He cast off his name, along with his dreaded reputation, and assumed a new identity. From then on, he posed as an outcast ship worker named Beauregard, who was in search of work without money or food. Quickly, the – to all appearances – starving man was nurtured by a wealthy family and hired as a servant. After a short time, however, the wealthy couple died of natural causes and Kuro served only their ailing daughter, Kaya. Since he liked the pirate-like life, he devised a plan to capture the family’s fortune without criminal-like fuss, and thus live out a prosperous and peaceful retirement in the village. For three long years he took care of the ailing Kaya, earning the trust of all the villagers, with only the great inheritance in mind. When Jango and his former crew finally showed up, he instructed him to hypnotize Kaya, have her sign a false will, and kill her. In order to make her death look like a robbery, the Black Cat pirate gang was also to loot the village.
Luffy and Usopp overheard this by chance and decided to save Kaya and the village. In fierce battles (1, 2, 3 and 4), the Straw Hat Pirates, with the help of Usopp, managed to defeat Kuro and his entourage and save Kaya’s life.
While Jango, defeated by Usopp knocked out in the forest, the gang already fled with the unconscious Kuro on their ship. Whether Black became captain of the gang again after awakening or disbanded it is unknown. Jango, however, who was left behind, ended his pirate life and joined the Navy after receiving a pardon.