Kayako Krieg and Sadashi Krieg are twin sisters. Their father, Dr. Hans Krieg, was once a colleague of Count Bavorové ze Strakonic, and they jointly engaged in cyberbrain research. After the revolution overthrew the kingdom of Eridu, Hans took his family and fled to the new colony. With the top secret research results he carried, Hans became the chief scientist of the Eden Foundation (EF) and was given a huge amount of resources to put his research into practical use.
Kayako is the younger of the twins by a few minutes. Their mother died during their escape from Eridu. Since then, Hans has buried himself in work, trying to forget the pain of the loss of his wife. EF has provided the best care to the Krieg family, treating them like royalty. However, the luxurious lifestyle and lack of parenting caused Kayako to become spoiled. She became more rebellious during puberty. Kayako was not grateful to her father for her material possessions, but was full of anger at him for ignoring their family. She began to vent her dissatisfaction through violence, often participating in gang fights. She was reckless and didn't care about getting hurt. She wanted to punish her father by showing him the wounds all over her body.
Kayako finally paid the price for her own recklessness: She was mortally injured in a fight, and her sister Sadashi was also struck down, while trying to save her. This made Hans very regretful, and he used all the resources he had available to try to save his daughters’ life. In the end, the board of directors of EF reached an agreement with him: EF would fund the transfer of Kayako and Sadashi’s brains to full cyborg bodies, using the achievement of Hans' cyberbrain technology. The exchange condition was that Kayako and Sadashi would participate in the combat cyborg test project being undertaken by the HOC.
Hans did not use ordinary cyborg bodies for the operation, but military cyborg bodies recovered by the HOC from the ruins of the old civilization. These biochemical bodies not only have powerful combat capabilities, but are also able to automatically adjust their parameters, according to the DNA of the human subject, in order to gain adaptive functions. The nano cells within the cyborg body will also continuously repair any damage to the human brain, which allows the host’s memory and personality to be perfectly preserved.
Kayako's character changed a lot after this near-death experience. She blamed herself for almost causing her sister's death and vowed to protect Sadashi for life. She began to cooperate with her father on his research, constantly improving her ability and skills on using her new body. However, as the combat test project deepened, she began to doubt the intentions of the EF and the HOC behind the scenes.
“Revive and restore for a better future.”
The purpose of the Eden Foundation(EF) is to recover advanced technologies from the old civilization. Despite its deep connection with the HOC (Honourable Omni Corporation), the foundation focuses more on information and knowledge than practical applications. Though more often than not, the foundation transfers useful devices and technologies they discover to HOC for military purposes. The Seireis are the key to opening the gate to the vast treasures of old mankind, so the foundation devotes great effort to finding such individuals.