Daiamondo wa kizutsukanai (1982)

With a title that roughly translates to “diamond that can never be damaged,” the scandalous erotic drama Daiamondo wa kizutsukanai (1987) recounts a taboo relationship between a young girl and a middle-aged teacher. Misako Tanaka stars as Yumiko Koshiya, the nubile young student that teacher Ichiro Mimura (Tsutomu Yamazaki) finds absolutely irresistible. Because of the scandalous nature of their relationship, Yumiko and Ichiro must now keep their trysts under wraps. Fortunately Tanaka doesn’t keep much else under wraps; the curvy Japanese beauty shows she’s up for anything as she treats her horny prof to a variety of intriguing positions.