Robson Zuccoli is the intensely loyal butler to Rebecca Rossellini, heiress and CEO of Italy's largest hotel chain. He prioritizes her safety and well-being above all, managing her daily affairs and shielding her from threats. While he initially disapproves of Rebecca's double life as a thrill-seeking thief, preferring her legitimate business and social duties, he consistently provides full support for her activities. Robson possesses advanced technological expertise, enabling him to hack security systems and implant discreet transmitters in Rebecca's clothing to monitor her safety. His skills also include hand-to-hand combat, proficiency with various weapons, and aircraft piloting.

During Rebecca's kidnapping and the Masked Count's challenge to Lupin III concerning the Cagliostro inheritance, Robson works actively to protect her, offering logistical support and direct intervention. He maintains a formal demeanor, though a subtle shift occurs; a conversation with Fujiko Mine implies Robson may derive personal satisfaction from aiding Rebecca's exploits despite his reluctance, suggesting a gradual, unspoken acceptance. His operational methods emphasize technological surveillance and strategic preparation, gathering intelligence and countering threats often from the background. His protective instincts drive decisive action using both tech and physical means when Rebecca faces danger. Robson steadfastly balances his traditional butler role with the demands of her unconventional lifestyle.