I'm trying to find an old hentai that was in the previews of another hentai on an old VHS called Hour of Darkness or something similar, in which a scientist used mutated plant DNA to extract fluids from schoolgirls.
The preview I'm looking for had something to do with a witch in a school, and that's about all I can remember. It's an older hentai, maybe late 80s- early 90s.