Yuko Yagisawa was sick as a child. Though she recovered, her devoutly religious parents sent her to a private school to quell her stubborn personality.

That school was Zenith Academy for Girls, where students got the best technology and "learned" the most advanced concepts, particularly in sex education. That is to say, the technology was used on the girls to tarnsform them into subservient slaves.

[From DLSite English]