Kojiro, known as James in localizations, experiences a significant transformation during the Pokémon: Black and White series. Promoted to Advanced Agent within Team Rocket's Unova operations, he adopts a new charcoal-gray uniform, replacing his traditional white attire. This uniform consists of a white long-sleeved shirt bearing a red "R," a black undershirt, white pants secured by a purple belt, and black boots with gloves. For covert activities, he conceals his identity under a navy blue trenchcoat, black glasses, and a gray fedora hat.

His personality shifts markedly, moving away from his usual lighthearted and emotional demeanor towards a more serious, stoic, and mission-driven focus. He demonstrates reduced concern for his Pokémon companions, family, or bystanders, aligning with Team Rocket's heightened objectives. This colder disposition is symbolized by his use of a black rose during Team Rocket mottos, replacing his former red rose. As an Advanced Agent, Kojiro participates in high-stakes missions directed by Giovanni and high-ranking operatives, executing elaborate schemes to capture Ash's Pikachu or other rare Pokémon, including one instance aboard a ship where his Amoonguss poisons Pikachu, later healed by wild Alomomola summoned by N.

Despite increased competence and resources, Team Rocket's core ineptitude resurfaces following the failure of the major Unova mission, "Operation Tempest." This failure results in Kojiro reverting to his pre-Unova personality—emotional, morally conflicted, and comically ineffective—and his uniform reverting to white.

Background elements like his wealthy Kanto origins, restrictive upbringing, flight from an arranged marriage to Jessebelle, his bond with his first Pokémon Growlie (a Growlithe), and estrangement from his parents remain consistent throughout but are not explored within the Unova-centric narrative.