Basilio is the Spanish dub name for Inspector Koichi Zenigata, the dedicated police officer who serves as the primary antagonist and pursuer of Arsène Lupin III. This name was used in the Spanish dubbing of the anime, particularly in the Telecinco broadcast in 1991. As a character, Basilio is an inspector with Interpol whose entire professional life revolves around capturing Lupin, whom he views as his personal and professional responsibility. His background is that of a seasoned, world-weary detective who has dedicated his career to bringing the elusive thief to justice, yet despite his best efforts and unwavering commitment, he never quite manages to succeed.

In terms of personality, Basilio is characterized by his intense passion and obsession with his work. He is often depicted as hot-headed, loud, and prone to dramatic outbursts of frustration whenever Lupin outsmarts him, which happens frequently. Despite his bombastic exterior, he possesses a strong sense of justice and integrity. He is not a corrupt or incompetent officer; rather, he is a highly skilled detective who is simply outmatched by Lupin's extraordinary cunning and resources. His motivations are clear and deeply personal: he seeks to uphold the law and restore his own honor by capturing the famous thief. This pursuit has become the central purpose of his life, blurring the line between professional duty and personal vendetta.

Basilio's role in the story is that of the eternal pursuer. He provides the constant cat-and-mouse dynamic that drives many of the plots, chasing Lupin and his associates across the globe. While he is officially the enemy of Lupin, the relationship is complex and has developed over time. Basilio has a grudging respect for Lupin's abilities, and on rare occasions when a greater threat emerges, he has been known to work alongside his quarry. The key relationship is, without a doubt, the one he shares with Lupin himself. This dynamic is often described as a game, one that both characters find engaging and even enjoyable. His relationships with the other members of Lupin's gang, including Oscar (Daisuke Jigen), Francis (Goemon Ishikawa XIII), and Patricia (Fujiko Mine), are purely functional, viewing them as accomplices to be apprehended alongside their leader.

Over the course of the various series and films, Basilio has shown little fundamental change in his core motivation, but the nature of his relationship with Lupin has deepened. What begins as a straightforward criminal versus detective chase evolves into something resembling a rivalry between two masters of their respective professions. There is an unspoken understanding and a bizarre sense of camaraderie born from their countless encounters. His development is seen in his occasional moments of doubt or reflection, questioning if his life's obsession has been worthwhile, though he ultimately reaffirms his commitment to the chase. As for notable abilities, Basilio is a remarkably competent investigator and hand-to-hand combatant. He is relentless and resourceful, possessing keen deductive skills. His signature technique is his expert use of handcuffs, which he can throw with remarkable accuracy to restrain opponents. However, his most defining ability is his incredible endurance and determination, allowing him to survive any number of humiliations and defeats only to resume his pursuit of Lupin immediately after.