Angel in the Dark.

Sato regular Koichi Imaizumi stars as a man obsessed with high school girls and their uniforms, viewing them as innocent and untainted. He begins an affair with one such girl (Yuri Ishihara), who is unmercifully bullied by her classmates and thus vulnerable to Imaizumi's attentions. After a time, Ishihara begins to manipulate her suitor, talking him into brutally raping all the girls who tormented her. Excited by schoolgirls as he is, Imaizumi has no problem acceding to Ishihara's demands at first, but eventually rebels due to his love for the vengeful nymphet.