Chief Kakuzawa, also referred to as Director Kakuzawa, is the main antagonist of the series and holds the position of head of the Diclonius Research Institute. He is an elderly man who presents himself to the Japanese government as a dedicated researcher working to contain the threat posed by the horned Diclonius. However, this public role is a complete deception that masks his true, genocidal ambitions. Kakuzawa is a psychopathic and fanatical individual driven by a delusional belief in his own racial superiority. His entire worldview is shaped by his family's long-held myth that they are descended from an ancient race of powerful Diclonius whose mighty bloodline was diluted over centuries of intermarriage with ordinary humans. He believes the emergence of modern Diclonius, particularly the powerful young woman designated Lucy, is absolute proof of this legend and represents the arrival of a long-awaited messiah who will restore his family's perceived rightful power. This conviction fuels his ultimate motivation: to eradicate humanity and replace it with a new world order dominated by Diclonius, with himself as the revered god and father of this new master race.

In his role at the Institute, Kakuzawa ruthlessly exploits the fears of the government to fund his research while secretly working to achieve the opposite of its intended purpose. His personal authority is vast, granting him access to elite military units like Japan's Special Assault Team, a privilege typically reserved for the Prime Minister. He is an utterly cold and manipulative figure who views everyone around him as disposable pawns, including his own family. He shows no emotional response to the death of his eldest son, Professor Kakuzawa, and he cruelly uses his subordinate, Dr. Kurama, by leveraging Kurama's forbidden love for his own Diclonius daughter, Mariko. Kakuzawa's depravity extends to his horrific treatment of Lucy's family; he captured and repeatedly raped her mother, forcing her to bear a male Diclonius child, who would be Lucy's half-brother. He intended for this boy and Lucy to serve as a new Adam and Eve for his planned world, ensuring the purity of the Diclonius bloodline through this forced union.

Throughout the story, Kakuzawa serves as the hidden mastermind orchestrating the tragic events that unfold. He is directly responsible for Lucy's dark transformation and suffering, having manipulated circumstances to isolate her and cultivate her hatred for humanity. Key relationships are defined entirely by his schemes. He maintains a complex dynamic with Dr. Kurama, whom he views as a valuable and obedient tool, but whose eventual moral awakening leads to defiance. His relationship with his own children is equally transactional; his elder son is a rival, his daughter Anna is transformed into a monstrous living computer for her predictive abilities, and his youngest son is a lobotomized prisoner kept as breeding stock. Despite his advanced age and lack of the telekinetic vectors that other Diclonius possess, Kakuzawa's true threat comes from his intellect, immense resources, and complete absence of empathy. His most notable accomplishments include the weaponization of the Diclonius birth virus, which he successfully spreads across the globe via a satellite payload to accelerate humanity's replacement. Kakuzawa's development is not one of growth but of escalating desperation as his plans near fruition. His defining end comes when he finally recaptures Lucy and reveals his master plan, only to have her reject it completely. In a final, crushing irony, Lucy reveals that the Kakuzawa family's legend was a lie; they are not Diclonius but simply humans with a minor cranial deformity. Kakuzawa, the man who dreamed of becoming a god, is decapitated by the very being he sought to control, his body swept away as his island fortress collapses.