Professor Kakuzawa is a relatively minor antagonist in Elfen Lied. He is the son of Director Kakuzawa, head of the Diclonius Research Institute. He works as a researcher for the Institute and as an instructor of biology at Kanagawa University. He is voiced by Hiroaki Hirata in the Japanese version and John Swasey in the English dub.
Not much is revealed about the Kakuzawa family in the Elfen Lied anime, but in the manga it is revealed that the Kakuzawa clan are descendants of the original Diclonii, a race of horned hominids with telekinetic powers that they used to commit murder. After many centuries since the original race died out, the Diclonius race began to re-emerge among humanity and the Kakuzawas, having gained tremendous wealth and power within the Japanese government, established their research institute in order to study these mutants. As far as the government were aware, the institute's main goal was to produce a vaccine to the genetic infection Diclonii transmit via their vectors, but in reality the Kakuzawas wanted to harness the Diclonius virus and spread it globally, ensuring the extinction of the old human race and the domination of the Diclonius over the earth.
Professor Kakuzawa joined his father's cause in bringing about Diclonius ascension, but had other ideas to bring the plan forward. Whereas the Director wanted to study the Diclonii like rats in a laboratory, the Professor wanted them unshackled and free to kill humans. He also wished to displace his father and become the master of this new race, and in order to achieve this goal, he secretly released the Diclonius "queen" known as Lucy.
In the fifth episode "Receipt", Professor Kakuzawa is teaching a class at the university and both Kouta and Yuka are attending. They bring Nyu with them so as not to leave her alone in Kaede House, but when Kakuzawa sees the Diclonius girl in his class, he cancels the class and demands that Yuka and Kouta relinquish custody of Nyu to him.
After hours, Kakuzawa has Nyu chained up in his lab and is prepared to rape her so that she can produce his new Diclonius children. He sedates her, but the sedative only puts one of the personalities to sleep. Nyu loses consciousness and the bitter, malevolent Lucy takes control. Kakuzawa tries to convince Lucy that he wants to help the Diclonii exterminate humanity and even shows her that he is actually a male Diclonius (though he has no vectors, only short horns that he hides under a wig). Lucy doesn't care for the professor's delusional scheming and decapitates him mid-rant.