The Kakuzawa family were direct descendants of the Original Diclonii, who believed themselves to be a species apart from other humans, and once thrived in feudal Japan. Because of their horns, they were discriminated against and regarded as demons and hunted down by non-horned humans. During the time they were persecuted, the Kakuzawas took refuge in a huge underground cave, at the bottom of a small island located off the coast of Kamakura. This island would later become the site of the Diclonius Research Institute. The research for this project was conducted by such people as the Kakuzawas, Kurama, Arakawa, Nousou and others at the Diclonius Research Institute. The head of the project was Chief Kakuzawa.
In order to learn the origin of Lucy, the Diconius "Queen", they searched for her birth parents. Upon capturing her mother, Kakuzawa learned she was the true mutant, having the ability to give birth to fully-reproductive Diclonii. Chief Kakuzawa raped and forced her to produce more "Monarch Diclonii". Only one Diclonius was born from this, a fully-reproductive male, Kaede's half-brother. The mother committed suicide to prevent her own further abuse and perhaps to stop Kakuzawa's plans. Despite dissecting the mother's reproductive organs, attempts at insemination and other methods, the boy remained the only true result. The Silpelit variety, like, Nana and Mariko Kurama, were capable of infecting human males with the virus and creating their offspring as Diclonii, but were sterile in and of themselves.
The project's first step was to infect all men worldwide with the Diclonius virus. This was accomplished by launching a rocket (under cover of a supposed satellite launch) carrying the virus and blowing it up over Kamakura, which unleashed the virus on a grand scale. It was predicted that in five years, the infection would spread worldwide, and that it would be the end of humanity. This was eventually stopped by the development of the Anti-Diclonius Birth Vaccine, developed by Professor Kakuzawa and Arakawa, though neither did so for altruistic reasons.
The second step was to hold Lucy, the Queen and only fertile female Diclonius, captive and force her to be the Mitochondrial Eve. Despite the Kakuzawas concocting it as their main objective, however, they had different ways of achieving it, with the initiator being the one calling the shots, at least in theory. For instance, Chief Kakuzawa wished that Lucy's half-brother be mated with her, to keep the bloodline pure, but his elder son, likely not knowing of the existence of the Male Diclonius, wished to himself be the "Adam" of the new race. To subvert his father's plans, he released her from her prison, in order to eventually find and rape her. However, when he was in a position to rape the helpless Nyu, Lucy woke up and killed him.
When Lucy was finally recaptured and brought to the Lebensborn Cave, Chief Kakuzawa explains to her that she is of his kind and the Messiah, the one with pure 'demon' blood who would restore his family to their former glory. He then shows her his son - her half-brother - and offers her his bloodline, a way to build a world of her own as opposed to one that would never accept her.
But Kaede rejected the counsel of her DNA instincts, feeling that she had found her place at the Maple House and instead kills the boy and Kakuzawa, ending the project of creating a new humanity. The island sank beneath the waves, with only the underground grotto remaining.
- Lebensborn was also the name of a eugenics project in Nazi Germany, which sought to breed "pure-blood Aryan" children and was also largely based on racial myths.
- The name was first mentioned in the series by Kakuzawa's elder son before he attempted to subvert his father's efforts and rape Lucy himself.
- The only Kakuzawas shown in the series to have a role in the project are the Chief, the Professor and Anna, but because the Kakuzawa family's generational goal is dominion over the Diclonii, it is possible that other members of the family were part of the project as well. A flashback showed her grandmother to be committed to the cause, and since the Unknown Man referred to the Diclonii as "we", including himself, it seems possible he was also a family member of some kind.