Director Kakuzawa is the primary antagonist of Elfen Lied, serving as the head of the Diclonius Research Institute. Publicly, his role is to manage the containment and study of Diclonius, a newly emerged race of horned individuals with dangerous telekinetic powers, a task he performs with the cooperation of the Japanese government. Privately, his motivations are the complete opposite. He is a power-hungry and egotistical man who seeks to wipe out humanity and establish a new world order where Diclonius are the dominant species, with himself as the patriarchal god of this new race. He is depicted as a fantatical and chillingly cold individual, willing to sacrifice anyone, including his own family, to achieve his goal. His personal authority is vast, granting him access to elite military units like the Special Assault Team, a privilege typically reserved for the Prime Minister.

Director Kakuzawa belongs to an ancient family that has passed down myths about being the original Diclonius. Members of his lineage possess small, vestigial horns hidden under their hair. However, unlike true Diclonius like Lucy, they have no vectors, the invisible arms that are the source of a Diclonius's power. His family's legend tells that their ancestors were powerful beings who were hunted by humans after their abilities were diluted through interbreeding. For generations, they prayed for the arrival of a pure-blooded messiah who would restore their lost power. When modern Diclonius began appearing, Kakuzawa became convinced that his family's myths were true and that the Diclonius queen, Lucy, was the long-awaited messiah. He founded the research institute on an island that served as a hiding place for his persecuted ancestors, using his position to manipulate events from the shadows.

His master plan centers on Lucy. He intends to mate with her to become the father of a new, pure Diclonius race that would inherit the Earth, granting him the status of a god. In pursuit of this, he is directly responsible for many of the series' tragedies. He manipulated Doctor Kurama, the on-site director of the facility, into carrying out his agenda, using Kurama's own Diclonius daughter, Mariko, as leverage. He also orchestrated the capture of Lucy's mother, whom he raped to produce a rare male Diclonius son, intended to be a breeding partner for Lucy should his own plans with her fail. Kakuzawa shows no genuine affection for his children. He displays disdain for his eldest son, Professor Kakuzawa, and is largely indifferent to his death. His daughter, Anna, was transformed into a monstrous, globe-like oracle capable of calculating complex probabilities to serve his schemes. He is manipulative to the core, using the loyalty and vulnerabilities of those around him, such as Kurama and Doctor Arakawa, as pawns in his grand design.

Over the course of the story, Kakuzawa remains a distant but ever-present threat. His actions indirectly cause Lucy's escape from the institute, setting the main plot in motion. As the series progresses, his true intentions are slowly revealed, culminating in the launch of a satellite that disperses a weaponized version of the Diclonius virus to infect women across the globe, ensuring the eventual replacement of humanity. His ultimate confrontation with Lucy occurs after she is recaptured. In a final attempt to win her over, he reveals his plans, including the existence of her half-brother, and explains her mother's tragic fate. However, Lucy rejects his ideology, revealing that his family were never true Diclonius but merely humans with a scalp mutation. She then decapitates him, and his final schemes, while personally thwarted, still succeed in setting the stage for a devastating future war.